Auto Body Surface Coating Guide

Auto Body Surface Coating:

A Practical Guide to Reducing Air

Emissions

Small Business Pollution Prevention Center

University of Northern Iowa


A Practical Guide to Reducing Air Emissions

Copyright 1998Iowa Waste Reduction CenterUniversity of Northern Iowa

Creation of this manual was funded by the U.S. Environmental Protection Agencyunder Cooperative Agreement CR 821492-01-4.


A Practical Guide to Reducing Air Emissions

Copyright 1998Iowa Waste Reduction CenterUniversity of Northern Iowa

Creation of this manual was funded by the U.S. Environmental Protection Agencyunder Cooperative Agreement CR 821492-01-4.

Table of Contents1. Introduction.........................................................................................................12. Auto Refinishing Process Overview...................................................................3

A. Recommended Steps for Practical Reduction of Air Emissions.................43. Spray Equipment ...............................................................................................7

A. Conventional Air Atomization Spray Equipment.......................................7Siphon Tube Feed Conventional Spray Guns .............................................8Gravity Fed Conventional Spray Guns .......................................................9

B. High-Volume / Low-Pressure (HVLP) Turbine ...........................................9C. High-Volume / Low-Pressure (HVLP) (non-turbine) ................................10

HVLP Spray Guns with Pressure Assist Cup...........................................10HVLP Gravity Fed Spray Guns .................................................................11HVLP Siphon Fed Spray Guns ..................................................................11

D. Low-Pressure / Low Volume (LPLV)..........................................................12E. Recommended Practices for Spray Equipment.........................................12

4. Spray Application Techniques..........................................................................13A. Recommended Practices for Spray Techniques.........................................17

5. Spray Equipment Cleaning..............................................................................19A. Manual Cleaning Processes .......................................................................19B. Pneumatically Powered Mechanical Cleaning Systems...........................20C. Recommended Practices for Spray Equipment Cleaning.........................21

6. Determining Product VOC Content ................................................................237. Surface Prep......................................................................................................25

A. Soap and Water...........................................................................................25B. Synthetic Reducers....................................................... ..............................25C. Solvent-Based Cleaners..............................................................................25D. Waterborne Cleaners .................................................................................26E. Recommended Practices for Surface Prep.................................................26

8. Undercoats........................................................................................................27A. Prep Coats...................................................................................................27

Metal Conditioners / Conversion Coatings ...............................................27Wash-Primers / Vinyl Wash-Primers.........................................................28Zinc Phosphate Primers .............................................................................28Self-Etching Primers ..................................................................................29Epoxy Primers.............................................................................................29Adhesion Promoters....................................................................................30Recommended Practices for Prep Coats....................................................30

B. Primer-Surfacers ........................................................................................30Acrylic Lacquer Primer-Surfacer...............................................................31Alkyd Synthetic Enamel Primer-Surfacer.................................................31Self-Etching Primers (as a Primer-Surfacer)............................................31One-Component Waterborne Primer-Surfacer..........................................32

The following individuals have volunteered to review the manual, Auto Body SurfaceCoating: A Practical Guide to Reducing Air Emissions.

Steve WiednerNortheast Iowa Community College, Calmar

Jim PhillipsHawkeye Community College

John ArnoldArnold’s Body Shop

Carl SuttonMcIntyre Oldsmobile-Cadillac, Inc.

Mark ClarkClark Supply Corporation

Ron ToyneKirkwood Community College

Table of Contents1. Introduction.........................................................................................................12. Auto Refinishing Process Overview...................................................................3

A. Recommended Steps for Practical Reduction of Air Emissions.................43. Spray Equipment ...............................................................................................7

A. Conventional Air Atomization Spray Equipment.......................................7Siphon Tube Feed Conventional Spray Guns .............................................8Gravity Fed Conventional Spray Guns .......................................................9

B. High-Volume / Low-Pressure (HVLP) Turbine ...........................................9C. High-Volume / Low-Pressure (HVLP) (non-turbine) ................................10

HVLP Spray Guns with Pressure Assist Cup...........................................10HVLP Gravity Fed Spray Guns .................................................................11HVLP Siphon Fed Spray Guns ..................................................................11

D. Low-Pressure / Low Volume (LPLV)..........................................................12E. Recommended Practices for Spray Equipment.........................................12

4. Spray Application Techniques..........................................................................13A. Recommended Practices for Spray Techniques.........................................17

5. Spray Equipment Cleaning..............................................................................19A. Manual Cleaning Processes .......................................................................19B. Pneumatically Powered Mechanical Cleaning Systems...........................20C. Recommended Practices for Spray Equipment Cleaning.........................21

6. Determining Product VOC Content ................................................................237. Surface Prep......................................................................................................25

A. Soap and Water...........................................................................................25B. Synthetic Reducers....................................................... ..............................25C. Solvent-Based Cleaners..............................................................................25D. Waterborne Cleaners .................................................................................26E. Recommended Practices for Surface Prep.................................................26

8. Undercoats........................................................................................................27A. Prep Coats...................................................................................................27

Metal Conditioners / Conversion Coatings ...............................................27Wash-Primers / Vinyl Wash-Primers.........................................................28Zinc Phosphate Primers .............................................................................28Self-Etching Primers ..................................................................................29Epoxy Primers.............................................................................................29Adhesion Promoters....................................................................................30Recommended Practices for Prep Coats....................................................30

B. Primer-Surfacers ........................................................................................30Acrylic Lacquer Primer-Surfacer...............................................................31Alkyd Synthetic Enamel Primer-Surfacer.................................................31Self-Etching Primers (as a Primer-Surfacer)............................................31One-Component Waterborne Primer-Surfacer..........................................32

The following individuals have volunteered to review the manual, Auto Body SurfaceCoating: A Practical Guide to Reducing Air Emissions.

Steve WiednerNortheast Iowa Community College, Calmar

Jim PhillipsHawkeye Community College

John ArnoldArnold’s Body Shop

Carl SuttonMcIntyre Oldsmobile-Cadillac, Inc.

Mark ClarkClark Supply Corporation

Ron ToyneKirkwood Community College

T he federal Clean Air ActAmendments (CAAA) of 1990 are

having a significant impact on smallbusinesses. New regulations arebeing proposed and implementedthat require air emission permits,and in many cases, expensive airemission control devices.

These new requirements have hada tremendous effect on howautomobile surface coating processesare performed. Specific chemicalsand materials used by the auto bodyindustry are targeted for regulationand control. The lists includechemicals known as Volatile OrganicCompounds (VOCs) and HazardousAir Pollutants (HAPs). Both VolatileOrganic Compounds and HazardousAir Pollutants are not only harmfulto the environment, but can alsocause severe health problems fort e ch n i c i a n s exposed to thesematerials.

◆ Volatile Organic Compounds (VOCs) are considered air pollutants because they create unwanted ozone smog in the lower

atmosphere. Many VOCs are also toxic to humans. Most organic

solvents used in the automotive painting industry are VOCs and emissions of these materials have fallen under new federal air regulations.

◆ Hazardous Air Pollutants ( H A P s ) are 189 materials listed bythe Environmental Protection

Agency (EPA), many of which aresolvents used in surface coatingo p e r a t i o n s. HAPs include toluene,x y l e n e, and methyl ethyl ketone.E v e n t u a l l y, all HAP emissions willbe subject to rigid standards andstrict controls.

The EPA has estimated that theautomobile refinishing industry alone is responsible for over 287,000tons of VOCs released in the U.S.every year. As much as 20 lbs of organic solvents may be emittedduring the surface coating of just onemedium-sized automobile.

Control systems have beendeveloped to help combat VOCemissions from surface coatingoperations. Many manufacturingfirms are currently using thesesystems in their paint booths toreduce VOC emissions by as much as95 percent. These add-on controlsinclude: Carbon Adsorption, ThermalIncineration, Catalytic Incineration,and Condensers.

Although proven effective in themanufacturing industry, emissioncontrol systems are extremelyexpensive, ranging from $20,000 to$70,000. For this reason, they areconsidered impractical for use incontrolling VOCs from small- tomedium-sized auto body repairshops. Currently the only practicalmeans of reducing the VOCs emittedfrom automobile refinishingoperations is to reduce the volume ofVOCs and HAPs being used. Thisrequires changes in products,equipment and applicationtechniques for auto refinishers.

Emission Reduction for Auto Body Shops1

1. Introduction

VOCs andHAPs

The Clean Air ActAmendments of1990 are signifi-cantly impactingsmall businesses

Epoxy Primer (as a Primer-Surfacer)........................................................32Polyester Primer-Surfacer..........................................................................32Acrylic Urethane Enamel Primer-Surfacer...............................................32Recommended Practices for Primer-Surfacers .........................................33

C. Primer-Sealers ............................................................................................33Lacquer Primer-Sealers..............................................................................33Enamel Type Primer-Sealers......................................................................33Single Component Waterborne Primer-Surfacer (as a Primer-Sealer)....34Epoxy Primer (as a Primer-Sealer)............................................................34Acrylic Urethane Primer-Sealers...............................................................34Recommended Practices for Primer-Sealers .............................................34

D. Sealers .........................................................................................................35Tie Coat Sealers..........................................................................................35Barrier Coat Sealers...................................................................................35Recommended Practices for Sealers..........................................................35

9. Top Coats ..........................................................................................................37A. Single Stage Topcoats.................................................................................38

Acrylic Lacquer............................................................................................38Alkyd Enamel..............................................................................................38Acrylic Enamel.............................................................................................39Polyurethane Enamel..................................................................................39Acrylic Urethane Enamel............................................................................39

B. Two Stage Basecoat / Clearcoat Topcoats .................................................40Waterborne Basecoat Systems...................................................................40Advantages of Waterborne Basecoat Systems ..........................................41Disadvantages of Waterborne Basecoat Systems .....................................42

C. Paint Additives ...........................................................................................42D. Recommended Practices for Topcoats .......................................................43

10. Recommended Approach to Practical Air Emissions Reduction...................4511. What to Expect in the Future.........................................................................49

T he federal Clean Air ActAmendments (CAAA) of 1990 are

having a significant impact on smallbusinesses. New regulations arebeing proposed and implementedthat require air emission permits,and in many cases, expensive airemission control devices.

These new requirements have hada tremendous effect on howautomobile surface coating processesare performed. Specific chemicalsand materials used by the auto bodyindustry are targeted for regulationand control. The lists includechemicals known as Volatile OrganicCompounds (VOCs) and HazardousAir Pollutants (HAPs). Both VolatileOrganic Compounds and HazardousAir Pollutants are not only harmfulto the environment, but can alsocause severe health problems fort e ch n i c i a n s exposed to thesematerials.

◆ Volatile Organic Compounds (VOCs) are considered air pollutants because they create unwanted ozone smog in the lower

atmosphere. Many VOCs are also toxic to humans. Most organic

solvents used in the automotive painting industry are VOCs and emissions of these materials have fallen under new federal air regulations.

◆ Hazardous Air Pollutants ( H A P s ) are 189 materials listed bythe Environmental Protection

Agency (EPA), many of which aresolvents used in surface coatingo p e r a t i o n s. HAPs include toluene,x y l e n e, and methyl ethyl ketone.E v e n t u a l l y, all HAP emissions willbe subject to rigid standards andstrict controls.

The EPA has estimated that theautomobile refinishing industry alone is responsible for over 287,000tons of VOCs released in the U.S.every year. As much as 20 lbs of organic solvents may be emittedduring the surface coating of just onemedium-sized automobile.

Control systems have beendeveloped to help combat VOCemissions from surface coatingoperations. Many manufacturingfirms are currently using thesesystems in their paint booths toreduce VOC emissions by as much as95 percent. These add-on controlsinclude: Carbon Adsorption, ThermalIncineration, Catalytic Incineration,and Condensers.

Although proven effective in themanufacturing industry, emissioncontrol systems are extremelyexpensive, ranging from $20,000 to$70,000. For this reason, they areconsidered impractical for use incontrolling VOCs from small- tomedium-sized auto body repairshops. Currently the only practicalmeans of reducing the VOCs emittedfrom automobile refinishingoperations is to reduce the volume ofVOCs and HAPs being used. Thisrequires changes in products,equipment and applicationtechniques for auto refinishers.


1. Introduction

VOCs andHAPs

The Clean Air ActAmendments of1990 are signifi-cantly impactingsmall businesses

Epoxy Primer (as a Primer-Surfacer)........................................................32Polyester Primer-Surfacer..........................................................................32Acrylic Urethane Enamel Primer-Surfacer...............................................32Recommended Practices for Primer-Surfacers .........................................33

C. Primer-Sealers ............................................................................................33Lacquer Primer-Sealers..............................................................................33Enamel Type Primer-Sealers......................................................................33Single Component Waterborne Primer-Surfacer (as a Primer-Sealer)....34Epoxy Primer (as a Primer-Sealer)............................................................34Acrylic Urethane Primer-Sealers...............................................................34Recommended Practices for Primer-Sealers .............................................34

D. Sealers .........................................................................................................35Tie Coat Sealers..........................................................................................35Barrier Coat Sealers...................................................................................35Recommended Practices for Sealers..........................................................35

9. Top Coats ..........................................................................................................37A. Single Stage Topcoats.................................................................................38

Acrylic Lacquer............................................................................................38Alkyd Enamel..............................................................................................38Acrylic Enamel.............................................................................................39Polyurethane Enamel..................................................................................39Acrylic Urethane Enamel............................................................................39

B. Two Stage Basecoat / Clearcoat Topcoats .................................................40Waterborne Basecoat Systems...................................................................40Advantages of Waterborne Basecoat Systems ..........................................41Disadvantages of Waterborne Basecoat Systems .....................................42

C. Paint Additives ...........................................................................................42D. Recommended Practices for Topcoats .......................................................43

10. Recommended Approach to Practical Air Emissions Reduction...................4511. What to Expect in the Future.........................................................................49

T he basic steps in automotiverefinishing include:

1. Prepaint surface cleaning:

Solvents are used for the removal ofcontaminants such as grease, t a r, wa x ,and silicone, all of which can have anadverse effect on the bond between thecoating and the substrate. Po o r l ycleaned surfaces result in finishimperfections or even the peeling ofthe topcoat from the substrate.Although these solvents are nottypically atomized for applicationp u r p o s e s, VOCs are released throughthe simple evaporation of the liquids o l v e n t s. Many of the solvents used forprepaint surface cleaning containtoluene and xylene. E a ch is listed as aVOC and HAP. In fact, most of thesecleaners contain 75 to 100 percentVO C s. E PA studies indicate theevaporation of these solvents accountsfor approximately 8 percent of the totalVOC emissions released during therefinishing process (see Figure 2).

2. Undercoat application:

The application of undercoats (prepc o a t s, p r i m e r- s u r f a c e r s, p r i m e r- s e a l e r s,and sealers) contributes significantlyto the volume of VOCs releasedduring surface coating operations.Undercoats generally contain lessthan 50 percent solvents by volume.However, because of the poor transferefficiency of the equipment and thenumber of coats typically applied,solvent based undercoats areresponsible for about 17 percent of allVOCs released during surface coating applications.

3. Application of the topcoat:

More than half of the VOCsreleased during the refinishingprocess occur during the top coatapplication, with metallics andlacquer finishes releasing the highestvolume. As with undercoats, theprimary reason for the high release ofVOCs in topcoat application is thepoor transfer efficiency of traditionalspray equipment. Less than one-halfof the topcoat material will be appliedto the desired surface using conven-tional spray equipment. The rest isexpelled as overspray.

4. Spray equipment cleaningo p e r a t i o n s :

Approximately 20 percent of VOCsreleased from auto refinishing occursduring equipment cleaningoperations. This figure reflects thevolume of organic solvents emitted tothe atmosphere during conventionalequipment cleaning (purging)procedures. The majority ofcommercial spray equipment cleanersfound on the market today are madeentirely of organic solvents.


Figure 2: EPA Estimates of VOC Emissions

Over half the VOCsreleased during therefinishing processare from top coatapplication

Topcoats (55%)Equipment Cleaning (20%)

Surface Prep (8%)Undercoats (17%)

1: Introduction


This Guide provides:• An overview of the auto refinishing process (Section 2) • A review of the spray equipment currently used for auto

refinishing operations (Section 3)• An outline of proper spray application processes (Section 4)• A look at spray equipment cleaning (purging) processes (Section 5)• Information on determining products’ VOC content (Section 6)• A review of surface prep cleaners (Section 7)• An overview of undercoats (Section 8)• A look at automotive topcoat systems (Section 9)• Recommended approach to practical air emission reduction (Section 10)• A projection of what to expect in the future (Section 11)

This practical pollution prevention guide was developed to helpautomotive refinishers:

• Reduce the amount of VOCs and HAPs emitted during painting operations

• Avoid the need for expensive ($20,000 - $70,000) emission controldevices

• Decrease the amount of paint-related wastes generated

• Maintain a high quality finish

In essence, "how to do more with less" in surface coating processes.

2. Auto RefinishingProcess Overview

T he basic steps in automotiverefinishing include:

1. Prepaint surface cleaning:

Solvents are used for the removal ofcontaminants such as grease, t a r, wa x ,and silicone, all of which can have anadverse effect on the bond between thecoating and the substrate. Po o r l ycleaned surfaces result in finishimperfections or even the peeling ofthe topcoat from the substrate.Although these solvents are nottypically atomized for applicationp u r p o s e s, VOCs are released throughthe simple evaporation of the liquids o l v e n t s. Many of the solvents used forprepaint surface cleaning containtoluene and xylene. E a ch is listed as aVOC and HAP. In fact, most of thesecleaners contain 75 to 100 percentVO C s. E PA studies indicate theevaporation of these solvents accountsfor approximately 8 percent of the totalVOC emissions released during therefinishing process (see Figure 2).

2. Undercoat application:

The application of undercoats (prepc o a t s, p r i m e r- s u r f a c e r s, p r i m e r- s e a l e r s,and sealers) contributes significantlyto the volume of VOCs releasedduring surface coating operations.Undercoats generally contain lessthan 50 percent solvents by volume.However, because of the poor transferefficiency of the equipment and thenumber of coats typically applied,solvent based undercoats areresponsible for about 17 percent of allVOCs released during surface coating applications.

3. Application of the topcoat:

More than half of the VOCsreleased during the refinishingprocess occur during the top coatapplication, with metallics andlacquer finishes releasing the highestvolume. As with undercoats, theprimary reason for the high release ofVOCs in topcoat application is thepoor transfer efficiency of traditionalspray equipment. Less than one-halfof the topcoat material will be appliedto the desired surface using conven-tional spray equipment. The rest isexpelled as overspray.

4. Spray equipment cleaningo p e r a t i o n s :

Approximately 20 percent of VOCsreleased from auto refinishing occursduring equipment cleaningoperations. This figure reflects thevolume of organic solvents emitted tothe atmosphere during conventionalequipment cleaning (purging)procedures. The majority ofcommercial spray equipment cleanersfound on the market today are madeentirely of organic solvents.



Over half the VOCsreleased during therefinishing processare from top coatapplication



1: Introduction


This Guide provides:• An overview of the auto refinishing process (Section 2) • A review of the spray equipment currently used for auto

refinishing operations (Section 3)• An outline of proper spray application processes (Section 4)• A look at spray equipment cleaning (purging) processes (Section 5)• Information on determining products’ VOC content (Section 6)• A review of surface prep cleaners (Section 7)• An overview of undercoats (Section 8)• A look at automotive topcoat systems (Section 9)• Recommended approach to practical air emission reduction (Section 10)• A projection of what to expect in the future (Section 11)

This practical pollution prevention guide was developed to helpautomotive refinishers:

• Reduce the amount of VOCs and HAPs emitted during painting operations

• Avoid the need for expensive ($20,000 - $70,000) emission controldevices

• Decrease the amount of paint-related wastes generated

• Maintain a high quality finish

In essence, "how to do more with less" in surface coating processes.

2. Auto RefinishingProcess Overview

2: Auto Refinishing Process Overview


Recommended Steps, con’tEQUIPMENT CLEANING •Use an air powered mechanical gun cleaning system.•Use low VOC cleaning solvents.

•If the guns are to be cleaned manually, spray into an enclosed backdrop to captureatomized solvents.

• Use a broom straw, cleaning broach, or a soft wood toothpick to clear passageways.

SURFACE PREP •Always wash dirt and grime from the vehicle using water or a soap and water

mixture.•Use waterborne cleaners when possible.•If, due to heavy contamination, waterborne cleaners prove unsatisfactory, use

solvent based cleaners for the initial cleaning. For secondary cleaning operations,use the waterborne products.

•If waterborne cleaners prove unsatisfactory due to substrate make-up, use solvent based cleaners sparingly.

•Keep solvent laden dirty rags in a closed container.• Keep solvent containers closed when not in use.

•Avoid operations that require multiple prepaint surface cleanings.

PREP COATS •Use versatile products such as epoxy primers or self-etching primers. The use of

these products may alleviate the need for additional surface coating operations such as primer-surfacing or primer-sealing.

•If a self-etching primer or epoxy primer is not desirable, use a wash-primer, or metal conditioner, conversion coating system.

•Avoid zinc-phosphate primers with high VOC content.

PRIMER-SURFACERS •Use a properly operating primer gun with the correct fluid tip/air cap combination

for your particular type of primer-surfacer.•Use low VOC waterborne primer-surfacer products.•If the curing time of waterborne products proves unsatisfactory, consider the use

of versatile urethane primers.• To reduce VOC emissions, limit material costs, and achieve a better quality product, perform body work using a minimal amount of primer-surfacer.• If a colored sealer is not used, make sure the primer-surfacer is a color that can

easily be covered with the desired topcoat.

See Section 5 forEquipment Cleaning

See Section 7 forSurface Prep

See Section 8.A forPrep Coat

See Section 8.B forPrimer-Surfacers



See Section 3 for SprayEquipment

See Section 4for Spray

ApplicationPractices

A. Recommended Steps for Practical Reduction of Air Emissions:

To reduce VOCs released during refinishing operations, facilities shoulduse the following recommended steps for practical air emission reduction:

SPRAY EQUIPMENT

•Determine the price range you are willing to spend for spray equipment.

• Determine the types of coatings that will be sprayed through the equipment, and the atomization properties required for proper application of these coatings.

•Prior to purchasing any paint gun, consult your paint representative to determine what type of gun works best for the application of the product you will be using.

•Contact your paint representative and/or spray gun representative to determine the fluid tip/air cap combination and gun settings recommended for the materials being sprayed.

• Choose spray equipment that will achieve the highest transfer efficiency while providing the required atomization properties within your price range.

SPRA Y APPLICATION PRACTICES

• Select the suggested air pressure and tip sizes for the specific product and equipment being used.

• Always hold the gun perpendicular to the surface being sprayed, using parallel strokes. Never arc the gun.

•Feather the trigger at the beginning and end of each pass.

•Use a 50 percent overlap for each pass. (Note: This technique may need to be altered slightly when applying high metallic, high solids basecoats, and some three stage systems.)

• When painting small and medium sized panels, make each pass the full length of the panel.

•With larger panels, use a comfortable stroke, with a 4 - 5 " overlap of the strokes.

• If blending is necessary, keep the blend area as small as possible without jeopardizing the appearance of the blend.

• Spray the border edges of the substrate first (banding). This will assure all edges are covered without extending the spray pattern well beyond the borders of the object.

• Use color hiding power labels to determine the thickness of the applied paint film.These markers will also indicate when adequate coverage has been achieved.



Recommended Steps, con’tEQUIPMENT CLEANING •Use an air powered mechanical gun cleaning system.•Use low VOC cleaning solvents.

•If the guns are to be cleaned manually, spray into an enclosed backdrop to captureatomized solvents.

• Use a broom straw, cleaning broach, or a soft wood toothpick to clear passageways.

SURFACE PREP •Always wash dirt and grime from the vehicle using water or a soap and water

mixture.•Use waterborne cleaners when possible.•If, due to heavy contamination, waterborne cleaners prove unsatisfactory, use

solvent based cleaners for the initial cleaning. For secondary cleaning operations,use the waterborne products.

•If waterborne cleaners prove unsatisfactory due to substrate make-up, use solvent based cleaners sparingly.

•Keep solvent laden dirty rags in a closed container.• Keep solvent containers closed when not in use.

•Avoid operations that require multiple prepaint surface cleanings.

PREP COATS •Use versatile products such as epoxy primers or self-etching primers. The use of

these products may alleviate the need for additional surface coating operations such as primer-surfacing or primer-sealing.

•If a self-etching primer or epoxy primer is not desirable, use a wash-primer, or metal conditioner, conversion coating system.

•Avoid zinc-phosphate primers with high VOC content.

PRIMER-SURFACERS •Use a properly operating primer gun with the correct fluid tip/air cap combination

for your particular type of primer-surfacer.•Use low VOC waterborne primer-surfacer products.•If the curing time of waterborne products proves unsatisfactory, consider the use

of versatile urethane primers.• To reduce VOC emissions, limit material costs, and achieve a better quality product, perform body work using a minimal amount of primer-surfacer.• If a colored sealer is not used, make sure the primer-surfacer is a color that can

easily be covered with the desired topcoat.

See Section 5 forEquipment Cleaning

See Section 7 forSurface Prep

See Section 8.A forPrep Coat

See Section 8.B forPrimer-Surfacers



See Section 3 for SprayEquipment

See Section 4for Spray

ApplicationPractices

A. Recommended Steps for Practical Reduction of Air Emissions:

To reduce VOCs released during refinishing operations, facilities shoulduse the following recommended steps for practical air emission reduction:

SPRAY EQUIPMENT

•Determine the price range you are willing to spend for spray equipment.

• Determine the types of coatings that will be sprayed through the equipment, and the atomization properties required for proper application of these coatings.

•Prior to purchasing any paint gun, consult your paint representative to determine what type of gun works best for the application of the product you will be using.

•Contact your paint representative and/or spray gun representative to determine the fluid tip/air cap combination and gun settings recommended for the materials being sprayed.

• Choose spray equipment that will achieve the highest transfer efficiency while providing the required atomization properties within your price range.

SPRA Y APPLICATION PRACTICES

• Select the suggested air pressure and tip sizes for the specific product and equipment being used.



•Use a 50 percent overlap for each pass. (Note: This technique may need to be altered slightly when applying high metallic, high solids basecoats, and some three stage systems.)





• Use color hiding power labels to determine the thickness of the applied paint film.These markers will also indicate when adequate coverage has been achieved.

P rior to the Clean Air Act, mosttechnicians chose spray

equipment based solely on its abilityto apply a quality finish. As thefocus on VOC emissions within therefinishing industry continues togrow, transfer efficiency has becomea major factor in spray equipmentselection.

Simply put, transfer efficiency isthe percentage of material atomizedthrough the gun that actually endsup as a coating on the desiredsurface. However, the transferefficiency of any type of sprayequipment is subject to change undera variety of conditions. Variablesaffecting transfer efficiency include:

• Technician's spraying technique• Size and configuration of the

object to be sprayed• Distance of the gun from the object

to be sprayed• Size of air cap and nozzle used• Air pressure at the tip• Volume of material exiting the gun

at the tip• Volume of air leaving the gun at

the tip• Viscosity of the material being

sprayed• Atmospheric conditions

(temperature, humidity and barometric pressure)

Spray gun manufacturers havedeveloped several new spraytechnologies in an attempt to achieveoptimum efficiency. While achievingexcellent transfer efficiency, many of

these new technologies were found tobe unacceptable for use in theapplication of automobile topcoats.Excess orange peel, pinholing,solvent popping, and mottling werecommon with many of these systems.Fortunately, a few of these newtechnologies proved capable ofproducing a high quality finish andthus are able to compete withconventional spray equipment in therefinishing industry. These newsystems include gravity fed conven-tional, high-volume/low-pressureturbine, high-volume/low-pressurenon-turbine, and low-pressure/low-volume spray guns.

A . Conventional A i rAtomization Spray Equipment

For decades, the conventionalsuction feed spray gun has been theoverwhelming favorite of automotiverefinishers worldwide. Thesesystems provide excellentatomization of the coating whilegiving the operator the controlneeded to achieve an even, high glossfinish. Conventional air guns rely onhigh pressure air (35 - 80 psi) toatomize the coating for application.This atomization of coatings takesplace in three separate stages.

1. The paint is surrounded by a highly pressurized column of air.This air column causes turbulenceto occur in the paint, which begins to separate the paint into small droplets.

2. The paint is then forced through the fluid nozzle of the gun. Air is released through containment holes in the air cap, enhancing theatomization of the fluid.


3. Spray Equipment

Transfer efficiency isa major factor inspray equipmentselection

The conventionalsuction feed spraygun has been theoverwhelming favoriteof auto refinishers



Recommended Steps, con’t

PRIMER-SEALERS •Use low VOC primer-sealers such as single component waterborne primers or

waterborne epoxy primers.• Use low VOC urethane primer-sealers as an alternative when possible.•Always choose a color of primer-sealer that can be easily covered with the topcoat

to be sprayed, or choose a tintable primer-sealer and tint it to an easily covered shade.

SEALERS • Choose the proper sealer for each specific job.•If filling capabilities are required, use a primer-sealer in place of a sealer.•Always choose a primer-sealer of a color that can be easily covered with the

coating to be sprayed, or choose a tintable primer-sealer.

TOPCOATS •Mix color coats in-house, making certain the formula for the proper shade of the

specific color code is used. This will help avoid the need for blending the finish to achieve a satisfactory color match.

•Keep good records of paint match information, including spray-out cards and detailed notes.

• Avoid the use of lacquer-based topcoats.•Choose low VOC topcoats that require fewer than three coats to achieve adequate

coverage (polyurethane or urethane).• Apply only the number of coats needed to achieve a quality finish.• Use high solids / low VOC clears to topcoat color coats.• Keep the use of paint additives to a minimum.•When available, use waterborne basecoats.

See Section8.C for

Primer-Sealers

See Section 8.Dfor Sealers

See Section 9 forTopcoats

P rior to the Clean Air Act, mosttechnicians chose spray

equipment based solely on its abilityto apply a quality finish. As thefocus on VOC emissions within therefinishing industry continues togrow, transfer efficiency has becomea major factor in spray equipmentselection.

Simply put, transfer efficiency isthe percentage of material atomizedthrough the gun that actually endsup as a coating on the desiredsurface. However, the transferefficiency of any type of sprayequipment is subject to change undera variety of conditions. Variablesaffecting transfer efficiency include:

• Technician's spraying technique• Size and configuration of the

object to be sprayed• Distance of the gun from the object

to be sprayed• Size of air cap and nozzle used• Air pressure at the tip• Volume of material exiting the gun

at the tip• Volume of air leaving the gun at

the tip• Viscosity of the material being

sprayed• Atmospheric conditions

(temperature, humidity and barometric pressure)

Spray gun manufacturers havedeveloped several new spraytechnologies in an attempt to achieveoptimum efficiency. While achievingexcellent transfer efficiency, many of

these new technologies were found tobe unacceptable for use in theapplication of automobile topcoats.Excess orange peel, pinholing,solvent popping, and mottling werecommon with many of these systems.Fortunately, a few of these newtechnologies proved capable ofproducing a high quality finish andthus are able to compete withconventional spray equipment in therefinishing industry. These newsystems include gravity fed conven-tional, high-volume/low-pressureturbine, high-volume/low-pressurenon-turbine, and low-pressure/low-volume spray guns.

A . Conventional A i rAtomization Spray Equipment

For decades, the conventionalsuction feed spray gun has been theoverwhelming favorite of automotiverefinishers worldwide. Thesesystems provide excellentatomization of the coating whilegiving the operator the controlneeded to achieve an even, high glossfinish. Conventional air guns rely onhigh pressure air (35 - 80 psi) toatomize the coating for application.This atomization of coatings takesplace in three separate stages.

1. The paint is surrounded by a highly pressurized column of air.This air column causes turbulenceto occur in the paint, which begins to separate the paint into small droplets.

2. The paint is then forced through the fluid nozzle of the gun. Air is released through containment holes in the air cap, enhancing theatomization of the fluid.


3. Spray Equipment

Transfer efficiency isa major factor inspray equipmentselection

The conventionalsuction feed spraygun has been theoverwhelming favoriteof auto refinishers



Recommended Steps, con’t

PRIMER-SEALERS •Use low VOC primer-sealers such as single component waterborne primers or

waterborne epoxy primers.• Use low VOC urethane primer-sealers as an alternative when possible.•Always choose a color of primer-sealer that can be easily covered with the topcoat

to be sprayed, or choose a tintable primer-sealer and tint it to an easily covered shade.

SEALERS • Choose the proper sealer for each specific job.•If filling capabilities are required, use a primer-sealer in place of a sealer.•Always choose a primer-sealer of a color that can be easily covered with the

coating to be sprayed, or choose a tintable primer-sealer.

TOPCOATS •Mix color coats in-house, making certain the formula for the proper shade of the

specific color code is used. This will help avoid the need for blending the finish to achieve a satisfactory color match.


• Avoid the use of lacquer-based topcoats.•Choose low VOC topcoats that require fewer than three coats to achieve adequate

coverage (polyurethane or urethane).• Apply only the number of coats needed to achieve a quality finish.• Use high solids / low VOC clears to topcoat color coats.• Keep the use of paint additives to a minimum.•When available, use waterborne basecoats.

See Section8.C for

Primer-Sealers

See Section 8.Dfor Sealers

See Section 9 forTopcoats

Gravity Fed Conventional SprayGuns

Gravity fed technology firstbecame popular with European autorefinishers for its ability to applyhigher viscosity coatings such asepoxy primers and high solids paintsand clears. As the use of thesecoatings has increased in the U.S., sohas the acceptance of gravity fedguns within the automobile repairindustry.

The major design differencebetween the gravity and siphon feddesigns is the location of the paintcup. The cup is located on top of thegravity fed guns, as opposed to thesiphon tube spray guns, which havethe cup located below the body of thegun. This cup location gives thegravity fed guns a distinct advantagein clearance over siphon fedequipment. This advantage becomesevident when spraying the lowerpanels of today's smallerautomobiles. Gravity fed spray gunsrely on gravity, not air pressure, tofeed the fluid to the gun. Higherviscosity solutions can be sprayedand atomized more effectively thanin siphon fed equipment.

Because of cup placement,virtually all the paint in the cup canbe used with little or no waste. Themajority of these cups are made of asemi-clear solvent-resistant plasticwhich gives the painter the addedadvantage of being able to see theamount of material left in thereservoir while spraying. Thetransfer efficiency of the gravity fedguns is slightly better due to thehigher viscosity material used,averaging approximately 40 percent.

Many painters adjust well to thegravity fed technology and can applyquality finishes with the first orsecond use. Others find adapting tothis type of equipment difficult.There are four specific obstacles thatmust be overcome to use gravity fedspray guns effectively. First, becauseof the gravity fed design of theseguns, as the paint level decreases, sodoes the rate of material feed.Although minor, the operator muststill adjust technique throughout thecoating process to compensate for thechange in fluid flow. Second, somepainters find that the highpositioning of the cup interferes withthe visibility of the surface duringcoating applications. Modificationsto a painter's spray technique maybe required to compensate for thisobstruction. Third, difficulties occurwhen spraying the underside of bodypanels. If the gun is pointedupwards, the material will not flowto the gun from the cup. Finally, thephysical design of the equipmentdoes not allow the operator to set thegun down without the aid of a standor spray gun hanger.

B. High-Volume/Low -Pressure (HVLP) Turbine

The HVLP turbine spray gunshave reportedly achieved transferefficiencies of 80 to 90 percent,exceeding all other automotiverefinishing spray equipment on themarket today (see Figure 3, pg 8).These systems use columns of lowpressure air to cause turbulencewithin the paint as the first stage ofatomization. The air used for thefinal step of atomization originatesfrom high-volume turbine drivenblowers. This air is heated to assist

3: Spray Equipment


HVLPTurbine Guns

3: Spray Equipment


3. Finally, air is released from the horns of the air cap and comes in contact with the atomized paint.This not only helps in the atomization process, but also shapes the paint pattern.

The sudden release of this highpressure air through the smallopenings of the nozzle breaks up thepaint and propels the spray awayfrom the gun. The atomizedmaterial is transferred to thesubstrate at a high velocity causingviolent air turbulence to occur at thesurface of the substrate. Thisturbulence forces much of theatomized material away from thesurface to be coated, resulting inmore than half of the atomized paintparticulates and solvents being lostas waste overspray.

Siphon Tube Feed ConventionalSpray Guns

The siphon tube spray gun hasbeen by far the favorite of auto bodyrefinishing technicians for bothundercoat and topcoat applications.

This equipment produces afully atomized paintpattern for even surfacecoverage and gives thecontrol needed for theapplication of metallicfinishes. The spraypattern allows even distri-bution of metallic flakesthroughout the substrateresulting in a finish free ofmetallic mottling flaws.The simple design of theseguns makes them veryeconomical to purchaseand maintain. A goodquality siphon tube spraygun costs from $120 -$300.

Depending on thematerial sprayed and the

pressure used, the transfer efficiencyof a siphon tube spray gun may be aslow as 35 percent. Sprayablematerial is lost through the exhaustsystem or as overspray on the boothfloor. Because air pressure is used topull the fluid from the cup to gun,only low viscosity coatings may beused effectively in these systems.The higher the material’s viscosity,the greater the air pressure requiredto draw the material up the siphontube. The higher the pressure, thegreater the amount of materialwasted as overspray. The siphondesign makes it impossible toretrieve all the paint from the cup, sothere will always be some unusedmaterial.

Figure 3: Transfer Efficiency of Spray Equipment

SiphonGravity

HVLP Turb

HVLP LPLV

Gravity Fed Conventional SprayGuns

Gravity fed technology firstbecame popular with European autorefinishers for its ability to applyhigher viscosity coatings such asepoxy primers and high solids paintsand clears. As the use of thesecoatings has increased in the U.S., sohas the acceptance of gravity fedguns within the automobile repairindustry.

The major design differencebetween the gravity and siphon feddesigns is the location of the paintcup. The cup is located on top of thegravity fed guns, as opposed to thesiphon tube spray guns, which havethe cup located below the body of thegun. This cup location gives thegravity fed guns a distinct advantagein clearance over siphon fedequipment. This advantage becomesevident when spraying the lowerpanels of today's smallerautomobiles. Gravity fed spray gunsrely on gravity, not air pressure, tofeed the fluid to the gun. Higherviscosity solutions can be sprayedand atomized more effectively thanin siphon fed equipment.

Because of cup placement,virtually all the paint in the cup canbe used with little or no waste. Themajority of these cups are made of asemi-clear solvent-resistant plasticwhich gives the painter the addedadvantage of being able to see theamount of material left in thereservoir while spraying. Thetransfer efficiency of the gravity fedguns is slightly better due to thehigher viscosity material used,averaging approximately 40 percent.

Many painters adjust well to thegravity fed technology and can applyquality finishes with the first orsecond use. Others find adapting tothis type of equipment difficult.There are four specific obstacles thatmust be overcome to use gravity fedspray guns effectively. First, becauseof the gravity fed design of theseguns, as the paint level decreases, sodoes the rate of material feed.Although minor, the operator muststill adjust technique throughout thecoating process to compensate for thechange in fluid flow. Second, somepainters find that the highpositioning of the cup interferes withthe visibility of the surface duringcoating applications. Modificationsto a painter's spray technique maybe required to compensate for thisobstruction. Third, difficulties occurwhen spraying the underside of bodypanels. If the gun is pointedupwards, the material will not flowto the gun from the cup. Finally, thephysical design of the equipmentdoes not allow the operator to set thegun down without the aid of a standor spray gun hanger.

B. High-Volume/Low -Pressure (HVLP) Turbine

The HVLP turbine spray gunshave reportedly achieved transferefficiencies of 80 to 90 percent,exceeding all other automotiverefinishing spray equipment on themarket today (see Figure 3, pg 8).These systems use columns of lowpressure air to cause turbulencewithin the paint as the first stage ofatomization. The air used for thefinal step of atomization originatesfrom high-volume turbine drivenblowers. This air is heated to assist

3: Spray Equipment


HVLPTurbine Guns

3: Spray Equipment


3. Finally, air is released from the horns of the air cap and comes in contact with the atomized paint.This not only helps in the atomization process, but also shapes the paint pattern.

The sudden release of this highpressure air through the smallopenings of the nozzle breaks up thepaint and propels the spray awayfrom the gun. The atomizedmaterial is transferred to thesubstrate at a high velocity causingviolent air turbulence to occur at thesurface of the substrate. Thisturbulence forces much of theatomized material away from thesurface to be coated, resulting inmore than half of the atomized paintparticulates and solvents being lostas waste overspray.

Siphon Tube Feed ConventionalSpray Guns

The siphon tube spray gun hasbeen by far the favorite of auto bodyrefinishing technicians for bothundercoat and topcoat applications.

This equipment produces afully atomized paintpattern for even surfacecoverage and gives thecontrol needed for theapplication of metallicfinishes. The spraypattern allows even distri-bution of metallic flakesthroughout the substrateresulting in a finish free ofmetallic mottling flaws.The simple design of theseguns makes them veryeconomical to purchaseand maintain. A goodquality siphon tube spraygun costs from $120 -$300.

Depending on thematerial sprayed and the

pressure used, the transfer efficiencyof a siphon tube spray gun may be aslow as 35 percent. Sprayablematerial is lost through the exhaustsystem or as overspray on the boothfloor. Because air pressure is used topull the fluid from the cup to gun,only low viscosity coatings may beused effectively in these systems.The higher the material’s viscosity,the greater the air pressure requiredto draw the material up the siphontube. The higher the pressure, thegreater the amount of materialwasted as overspray. The siphondesign makes it impossible toretrieve all the paint from the cup, sothere will always be some unusedmaterial.

Figure 3: Transfer Efficiency of Spray Equipment

SiphonGravity

HVLP Turb

HVLP LPLV

separate regulated air line, to feedthe paint to the gun. Thepressurized cup improves thetransfer efficiency of the gun.

As with any pressurized paint gun,care must be taken not to over-pressurize the paint cup or remove apressurized cup.Equipment damage oroperator injury mayr e s u l t . Some atomizationproblems may also beexperienced when sprayingepoxy primers and highsolids coatings due to theirhigh viscosity.

HVLP Gravity Fed SprayGuns

The gravity fed HVLPguns (see Figure 4)combine the finestqualities of the HVLP andconventional gravity fedspray guns into one design.Like its conventional counterpart,these guns work especially well onhigh solids and water-based paints,clears, and primers due to their topmounting, gravity fed material cup.

This design also shares thedisadvantages of its conventionalcounterpart; as the paint leveldecreases, so does the feed rate.Therefore, the operator must adjusttechnique to compensate for thechange in fluid flow.

HVLP Siphon Fed Spray Guns

To gain acceptance in the autorefinishing industry, some spray gunmanufacturers are producing siphonfed HVLP spray equipment. The

siphon fed spray guns come as closeas any of the HVLP equipment tolooking and feeling like a conven-tional siphon spray gun. Somecompanies are even producingconversion kits to make a conven-tional siphon fed into an HVLP

siphon feed gun. This makes theprice of this HVLP technologyextremely affordable. These gunsproduce basically the same soft spraypattern as all HVLP guns withatomizing pressures as low as 5 psi.The siphon design has a lowertransfer efficiency than other HVLPtechnologies.

D. Low-Pressure/Low- Vo l u m e(LPLV)

Another spray technologydeveloped to improve transferefficiency is the Low-Pressure/Low-Volume (LPLV) spray equipment.

3: Spray Equipment


Figure 4: HVLP Gravity Fed Spray Gun

3: Spray Equipment


in the atomization process and istransferred to the gun using largediameter air lines. The air is used toatomize the paint in basically thesame manner as a conventional gun,but is much more efficient. Theturbine supplies all the air neededfor the system to operate. No outsideair source is required.

HVLP turbine spray guns have somedistinct disadvantages.

• The cost of these systems is high,with price tags commonly exceeding $3,000.

• The large air lines are often cumbersome for the operator.

• Blending metallic finishes is very difficult using the HVLP system due to the heavy application coats.

• The atomization of the turbine HVLP spray guns may not give t h e quality finish required to match automotive factory finishes.

C. High-Volume/Low-Pressure (HVLP) (non-turbine)

The problems of the HVLP turbinein automotive refinishing werequickly realized by the spray gunmanufacturers. To help alleviatesome of these downfalls, manufac-turers developed more versatile, lessexpensive HVLP spray equipment.Depending on the make of gun, thesesystems have a transfer efficiencyranging from 55 - 75 percent, andreport a savings in material of 20 -30 percent over conventional sprayguns. The non-turbine HVLP gunsuse only conventional shop air fortheir operations. No expensive

auxiliary air supply sources orturbines are needed. These sprayguns do require high volumes of air(13 - 30 cfm at 10 psi), so at least afive horsepower compressor, withadequate piping (i.e. 3/4") is usuallyrequired to supply the needed volumeof air. As with all non-turbine lowpressure spray equipment, incomingair must be dry to prevent watercondensation within the gun.

The non-turbine HVLP technologyhas proved to be a vast improvementover the turbine models, but it stillhas obstacles that must be overcome.The application rates of the HVLPsystems are much slower than thatof conventional spray equipment.Also, non-turbine HVLP spray gunsdo not offer the metallic control ofconventional style guns, making thespraying of metallic topcoats difficultto master. As with all HVLP sprayequipment, non-turbine models clogeasily. For this reason, coatingmaterial filtration and proper guncleaning practices are essential.Finally, blending topcoats using theHVLP technology has been achallenge for painters. The thickcoats applied using the HVLP gunsdo not produce the gradual taperingeffect needed for blending of highsolid and metallic topcoats.

HVLP Spray Guns With PressureAssist Cup

One attempt to improve the HVLPtechnology to better suit the autorepair industry was the addition of apressure cup to the system. Thesesystems use a paint cup mountedunder the gun, similar to a conven-tional spray gun design. With thisstyle, the cup is pressurized, using a

HVLP Non-Turbine Guns

separate regulated air line, to feedthe paint to the gun. Thepressurized cup improves thetransfer efficiency of the gun.

As with any pressurized paint gun,care must be taken not to over-pressurize the paint cup or remove apressurized cup.Equipment damage oroperator injury mayr e s u l t . Some atomizationproblems may also beexperienced when sprayingepoxy primers and highsolids coatings due to theirhigh viscosity.

HVLP Gravity Fed SprayGuns

The gravity fed HVLPguns (see Figure 4)combine the finestqualities of the HVLP andconventional gravity fedspray guns into one design.Like its conventional counterpart,these guns work especially well onhigh solids and water-based paints,clears, and primers due to their topmounting, gravity fed material cup.

This design also shares thedisadvantages of its conventionalcounterpart; as the paint leveldecreases, so does the feed rate.Therefore, the operator must adjusttechnique to compensate for thechange in fluid flow.

HVLP Siphon Fed Spray Guns

To gain acceptance in the autorefinishing industry, some spray gunmanufacturers are producing siphonfed HVLP spray equipment. The

siphon fed spray guns come as closeas any of the HVLP equipment tolooking and feeling like a conven-tional siphon spray gun. Somecompanies are even producingconversion kits to make a conven-tional siphon fed into an HVLP

siphon feed gun. This makes theprice of this HVLP technologyextremely affordable. These gunsproduce basically the same soft spraypattern as all HVLP guns withatomizing pressures as low as 5 psi.The siphon design has a lowertransfer efficiency than other HVLPtechnologies.

D. Low-Pressure/Low- Vo l u m e(LPLV)

Another spray technologydeveloped to improve transferefficiency is the Low-Pressure/Low-Volume (LPLV) spray equipment.

3: Spray Equipment


Figure 4: HVLP Gravity Fed Spray Gun

3: Spray Equipment


in the atomization process and istransferred to the gun using largediameter air lines. The air is used toatomize the paint in basically thesame manner as a conventional gun,but is much more efficient. Theturbine supplies all the air neededfor the system to operate. No outsideair source is required.

HVLP turbine spray guns have somedistinct disadvantages.

• The cost of these systems is high,with price tags commonly exceeding $3,000.

• The large air lines are often cumbersome for the operator.

• Blending metallic finishes is very difficult using the HVLP system due to the heavy application coats.

• The atomization of the turbine HVLP spray guns may not give t h e quality finish required to match automotive factory finishes.

C. High-Volume/Low-Pressure (HVLP) (non-turbine)

The problems of the HVLP turbinein automotive refinishing werequickly realized by the spray gunmanufacturers. To help alleviatesome of these downfalls, manufac-turers developed more versatile, lessexpensive HVLP spray equipment.Depending on the make of gun, thesesystems have a transfer efficiencyranging from 55 - 75 percent, andreport a savings in material of 20 -30 percent over conventional sprayguns. The non-turbine HVLP gunsuse only conventional shop air fortheir operations. No expensive

auxiliary air supply sources orturbines are needed. These sprayguns do require high volumes of air(13 - 30 cfm at 10 psi), so at least afive horsepower compressor, withadequate piping (i.e. 3/4") is usuallyrequired to supply the needed volumeof air. As with all non-turbine lowpressure spray equipment, incomingair must be dry to prevent watercondensation within the gun.

The non-turbine HVLP technologyhas proved to be a vast improvementover the turbine models, but it stillhas obstacles that must be overcome.The application rates of the HVLPsystems are much slower than thatof conventional spray equipment.Also, non-turbine HVLP spray gunsdo not offer the metallic control ofconventional style guns, making thespraying of metallic topcoats difficultto master. As with all HVLP sprayequipment, non-turbine models clogeasily. For this reason, coatingmaterial filtration and proper guncleaning practices are essential.Finally, blending topcoats using theHVLP technology has been achallenge for painters. The thickcoats applied using the HVLP gunsdo not produce the gradual taperingeffect needed for blending of highsolid and metallic topcoats.

HVLP Spray Guns With PressureAssist Cup

One attempt to improve the HVLPtechnology to better suit the autorepair industry was the addition of apressure cup to the system. Thesesystems use a paint cup mountedunder the gun, similar to a conven-tional spray gun design. With thisstyle, the cup is pressurized, using a

HVLP Non-Turbine Guns

B oth the quality of the finish andtransfer efficiency greatly depend

on the technician’s skill and sprayingt e ch n i q u e s. Cost and sophisticationof paint application equipment do notensure a quality finish. In order toachieve a quality finish, the paintermust focus on the proper combinationof the following variables:

• Type of material to be sprayed• Viscosity of material• Thinner/reducer speed used• Type of hardener or reactor used• Addition of additives• Booth air temperature• Booth air flow• Paint gun orifice size• Paint gun air cap style• Paint gun adjustments (air, fluid,

fan size)• Distance of the spray gun from

surface• Operator's spray gun speed

According to a study done by thePacific Northwest PollutionPrevention Research Center,"Transfer Efficiency and VOCEmissions of Spray Gun CoatingTechnologies in Wood Finishing", theVOC emissions released during asurface coating process are directlyrelated to the skill of the spray gunoperator. The study concluded that"the difference in transfer efficiencydue to painter skill level with asingle gun type were often largerthan the differences between guntypes." In other words, properpainting technique is often moreimportant than high transferefficient spray equipment when itcomes to reducing emissions. Askilled technician will adjustspraying style with each specific jobto compensate for the type of coatingbeing sprayed, the atmosphericconditions, the size and shape of theobject being coated and the sprayequipment used. Due to all thevariables involved, it is impossible tospecify the one best spray techniquefor all situations.


4. Spray ApplicationTechniques

The quality of thefinish and transferefficiency depend on thskill and technique ofthe technician

Painting technique isoften more importantthan transfer efficientspray equipment inreducing emissions

In general, technicians should follow these basic rules.

A. Always have the correct gun setup for the coating to be sprayed and the size ofthe area to be covered. These variables include the size of fluid tip and air capused. Fluid tip size is determined by the viscosity of the coating as well as theflow rate setting of the gun. The viscosity is determined using a Zahn cupmeasuring system (see figure 5, pg 14).

The flow rate can be determined through the following process:

For pressure fed spray equipment:

1. Turn off the atomizing air.2. Aim spray gun tip towards a container (preferably a graduated container).3. Pull the trigger of the gun, spraying the unatomized coating into the container

for 60 seconds.4. Measure the amount of material expelled from the gun into the container to

determine the flow rate in ounces/minute.

3: Spray Equipment


Like the HVLP equipment, L P LVguns use conventional shop air anddo not require expensive turbineu n i t s. The LPLV spray guns requireonly 7 - 8 cfm of compressed air at10 psi (as opposed to the 13 - 30 cfmrequired for HVLP equipment).Unlike HVLP equipment, the firststage of atomization occurs withinthe LPLV spray gun. Air and paintare mixed inside an internal ch a m b e rof the air cap to further assist in thepaint atomization. The LPLVsystems boast a transfer efficiencyranging from 55 - 75 percent.

As with all the new sprayt e ch n o l o g i e s, the LPLV systems hav eo b s t a cles that the painter musto v e r c o m e. Among these is a

pressurized cup, used in some LPLVs y s t e m s, w h i ch is only pressurizedwhen the gun trigger is pulled.Some changes in spray tech n i q u em ay be required to accommodatethis delay in material delivery.L P LV spray equipment has gainedonly minimal acceptance in theautomobile refinishing industry.

Prior to purchasing any paintg u n , consult your paint represen-tative to determine which type ofgun will work best for theapplication of the product you willu s e. Your paint and/or spray gunrepresentative can also help youdetermine the proper fluid tip/aircap combination and proper guns e t t i n g s.

E. Recommended Practices for Spray Equipment•Determine the price range you are willing to spend for spray equipment.

•Determine the types of coatings that will be sprayed through the equipment and the atomization properties required for their proper application.

•Choose spray equipment that will achieve the highest transfer efficiency while providing the required atomization properties within your price range.

•Prior to purchasing any paint gun, consult your paint representative to determine what type of gun will work best for the application of the product you will be using.

•Contact your paint representative and/or spray gun representative to determine the fluid tip/air cap combination and gun settings that should be used with the material being sprayed.

LPLV Guns

B oth the quality of the finish andtransfer efficiency greatly depend

on the technician’s skill and sprayingt e ch n i q u e s. Cost and sophisticationof paint application equipment do notensure a quality finish. In order toachieve a quality finish, the paintermust focus on the proper combinationof the following variables:

• Type of material to be sprayed• Viscosity of material• Thinner/reducer speed used• Type of hardener or reactor used• Addition of additives• Booth air temperature• Booth air flow• Paint gun orifice size• Paint gun air cap style• Paint gun adjustments (air, fluid,

fan size)• Distance of the spray gun from

surface• Operator's spray gun speed

According to a study done by thePacific Northwest PollutionPrevention Research Center,"Transfer Efficiency and VOCEmissions of Spray Gun CoatingTechnologies in Wood Finishing", theVOC emissions released during asurface coating process are directlyrelated to the skill of the spray gunoperator. The study concluded that"the difference in transfer efficiencydue to painter skill level with asingle gun type were often largerthan the differences between guntypes." In other words, properpainting technique is often moreimportant than high transferefficient spray equipment when itcomes to reducing emissions. Askilled technician will adjustspraying style with each specific jobto compensate for the type of coatingbeing sprayed, the atmosphericconditions, the size and shape of theobject being coated and the sprayequipment used. Due to all thevariables involved, it is impossible tospecify the one best spray techniquefor all situations.


4. Spray ApplicationTechniques

The quality of thefinish and transferefficiency depend on thskill and technique ofthe technician

Painting technique isoften more importantthan transfer efficientspray equipment inreducing emissions

In general, technicians should follow these basic rules.

A. Always have the correct gun setup for the coating to be sprayed and the size ofthe area to be covered. These variables include the size of fluid tip and air capused. Fluid tip size is determined by the viscosity of the coating as well as theflow rate setting of the gun. The viscosity is determined using a Zahn cupmeasuring system (see figure 5, pg 14).

The flow rate can be determined through the following process:

For pressure fed spray equipment:

1. Turn off the atomizing air.2. Aim spray gun tip towards a container (preferably a graduated container).3. Pull the trigger of the gun, spraying the unatomized coating into the container

for 60 seconds.4. Measure the amount of material expelled from the gun into the container to

determine the flow rate in ounces/minute.

3: Spray Equipment


Like the HVLP equipment, L P LVguns use conventional shop air anddo not require expensive turbineu n i t s. The LPLV spray guns requireonly 7 - 8 cfm of compressed air at10 psi (as opposed to the 13 - 30 cfmrequired for HVLP equipment).Unlike HVLP equipment, the firststage of atomization occurs withinthe LPLV spray gun. Air and paintare mixed inside an internal ch a m b e rof the air cap to further assist in thepaint atomization. The LPLVsystems boast a transfer efficiencyranging from 55 - 75 percent.

As with all the new sprayt e ch n o l o g i e s, the LPLV systems hav eo b s t a cles that the painter musto v e r c o m e. Among these is a

pressurized cup, used in some LPLVs y s t e m s, w h i ch is only pressurizedwhen the gun trigger is pulled.Some changes in spray tech n i q u em ay be required to accommodatethis delay in material delivery.L P LV spray equipment has gainedonly minimal acceptance in theautomobile refinishing industry.

Prior to purchasing any paintg u n , consult your paint represen-tative to determine which type ofgun will work best for theapplication of the product you willu s e. Your paint and/or spray gunrepresentative can also help youdetermine the proper fluid tip/aircap combination and proper guns e t t i n g s.

E. Recommended Practices for Spray Equipment•Determine the price range you are willing to spend for spray equipment.


•Choose spray equipment that will achieve the highest transfer efficiency while providing the required atomization properties within your price range.

•Prior to purchasing any paint gun, consult your paint representative to determine what type of gun will work best for the application of the product you will be using.

•Contact your paint representative and/or spray gun representative to determine the fluid tip/air cap combination and gun settings that should be used with the material being sprayed.

LPLV Guns

4: Spray Application Techniques


Figure 7: Proper Spray Distance and Technique

Figure 8: 50% Overlap Technique

6 - 8”

The spray gun should be held 6-8”from the substrate

The painter shoulduse a 50% overlapfor each pass

F. The spray gun should be held at a distance of 6 - 8" from the substrate, andthis distance should be maintained with each stroke (Figure 7). In general, t h ep a i n t e r should use a 50 percent overlap for each pass, feathering the trigger atthe beginning and end of each stroke (Figure 8). This technique may need to bealtered slightly when applying high-metallic, high-solids basecoats and for somethree stage systems to avoid striping. The speed of each pass should be acomfortable pace for the technician while maintaining a full wet coat, free of sagsor runs.

For siphon fed spray equipment:

1 . Measure the amount of material in the sprayc u p2 . Pull the trigger of the gun, s p r aying the gunat normal operating settings for 60 seconds.3 . Measure the amount of material left in thes p r ay cup to determine the volume of materials p r ayed per minute.

B . Once the proper fluid tip size has beendetermined, an air cap can be chosen. Thechoice of an air cap depends on fluid tip sizeand the desired air consumption of the gun.Many paint gun manufacturers have fluidtip/air cap combinations preset to helpdetermine the proper pairing. Because fluidtips and air nozzles are precision machined tovery stringent tolerances, it is important thattheir orifices remain free from obstructions toassure proper atomization and spray patternuniformity.

C. Set the air pressure at the lowest possible setting that will provide therequired degree of atomization. Too low of a setting may result in a heavycentered spray pattern. Too high of a pressure setting will cause a dry spraypattern, resulting in a dry rough finish. Never exceed the coating manufacturer’srecommended air pressure settings.

D. The size of the fan pattern will vary with the size and configuration of thesurface to be coated. For small spot repair operations, a small pattern is usuallypreferable. For large panels, a full pattern is generally the most desirable setting.

E . When spraying, always hold the gun perpendicular to the surface beingsprayed, using parallel strokes. Never arc the spray gun (Figure 6), with twonotable exceptions:

◆ s p r aying extremely large panels that exceed the length of the painters reach .In these cases, the painter will arc the gun at the end of the pass tohelp blend the overlap a r e a s, a n d

◆ performing panel spotting or blending o p e r a t i o n s.



Figure 5: Zahn Cup

Figure 6: Improper Spray Technique

Always hold thegun perpendicular to

the substrate



Figure 7: Proper Spray Distance and Technique

Figure 8: 50% Overlap Technique

6 - 8”

The spray gun should be held 6-8”from the substrate

The painter shoulduse a 50% overlapfor each pass

F. The spray gun should be held at a distance of 6 - 8" from the substrate, andthis distance should be maintained with each stroke (Figure 7). In general, t h ep a i n t e r should use a 50 percent overlap for each pass, feathering the trigger atthe beginning and end of each stroke (Figure 8). This technique may need to bealtered slightly when applying high-metallic, high-solids basecoats and for somethree stage systems to avoid striping. The speed of each pass should be acomfortable pace for the technician while maintaining a full wet coat, free of sagsor runs.

For siphon fed spray equipment:

1 . Measure the amount of material in the sprayc u p2 . Pull the trigger of the gun, s p r aying the gunat normal operating settings for 60 seconds.3 . Measure the amount of material left in thes p r ay cup to determine the volume of materials p r ayed per minute.

B . Once the proper fluid tip size has beendetermined, an air cap can be chosen. Thechoice of an air cap depends on fluid tip sizeand the desired air consumption of the gun.Many paint gun manufacturers have fluidtip/air cap combinations preset to helpdetermine the proper pairing. Because fluidtips and air nozzles are precision machined tovery stringent tolerances, it is important thattheir orifices remain free from obstructions toassure proper atomization and spray patternuniformity.

C. Set the air pressure at the lowest possible setting that will provide therequired degree of atomization. Too low of a setting may result in a heavycentered spray pattern. Too high of a pressure setting will cause a dry spraypattern, resulting in a dry rough finish. Never exceed the coating manufacturer’srecommended air pressure settings.

D. The size of the fan pattern will vary with the size and configuration of thesurface to be coated. For small spot repair operations, a small pattern is usuallypreferable. For large panels, a full pattern is generally the most desirable setting.

E . When spraying, always hold the gun perpendicular to the surface beingsprayed, using parallel strokes. Never arc the spray gun (Figure 6), with twonotable exceptions:

◆ s p r aying extremely large panels that exceed the length of the painters reach .In these cases, the painter will arc the gun at the end of the pass tohelp blend the overlap a r e a s, a n d

◆ performing panel spotting or blending o p e r a t i o n s.



Figure 5: Zahn Cup

Figure 6: Improper Spray Technique

Always hold thegun perpendicular to

the substrate



A. Recommended Practices for Spray Application Techniques•Use the suggested air pressure and tip sizes for the specific product and

equipment being used.

•Always hold gun perpendicular to the surface being sprayed, using parallel strokes. Never arc the gun.


•Use a 50 percent overlap for each pass. This technique may need to be altered slightly when applying high-metallic, high-solids basecoats and some three stage systems.

•When painting small- and medium-sized panels, make each pass the full length of the panel.


•If blending is necessary, keep the blend area as small as possible without jeopardizing the appearance of the blend.

•Spray the border edges of the substrate first (banding). This will assure all edges are covered without extending the spray pattern well beyond theborders of the object.

•Use color hiding power labels to determine the thickness of the applied paint film. These markers will also indicate when adequate coverage has been achieved.



Figure 9: Banding

Figure 10: Self-Adhering Power Label

Always paintsmall and mediumsize panels withoutbreaking the stroke

G. Always paint small and medium size panels without breaking the stroke. Withlarger panels, use a 4 - 5" overlap of the strokes, arcing the gun at the end of eachpass. When spotting or blending a panel, keep the blend as small as possiblewithout jeopardizing the appearance of the blend. To help insure proper coverageof edges while reducing overspray, spray the outer boundaries of the panel first.This technique, called banding, allows the painter to maintain adequate coverageat the edges of the panel without extending the spray stroke well beyond the endof the panel surface (Figure 9).

When applying a topcoat, use hiding power labels to determine when thesurface has been adequately covered. Through the use of these labels, thetechnician can be assured of achieving proper coverage without the application ofexcess material (Figure 10).



A. Recommended Practices for Spray Application Techniques•Use the suggested air pressure and tip sizes for the specific product and


•Always hold gun perpendicular to the surface being sprayed, using parallel strokes. Never arc the gun.


•Use a 50 percent overlap for each pass. This technique may need to be altered slightly when applying high-metallic, high-solids basecoats and some three stage systems.

•When painting small- and medium-sized panels, make each pass the full length of the panel.


•If blending is necessary, keep the blend area as small as possible without jeopardizing the appearance of the blend.

•Spray the border edges of the substrate first (banding). This will assure all edges are covered without extending the spray pattern well beyond theborders of the object.

•Use color hiding power labels to determine the thickness of the applied paint film. These markers will also indicate when adequate coverage has been achieved.



Figure 9: Banding

Figure 10: Self-Adhering Power Label

Always paintsmall and mediumsize panels withoutbreaking the stroke

G. Always paint small and medium size panels without breaking the stroke. Withlarger panels, use a 4 - 5" overlap of the strokes, arcing the gun at the end of eachpass. When spotting or blending a panel, keep the blend as small as possiblewithout jeopardizing the appearance of the blend. To help insure proper coverageof edges while reducing overspray, spray the outer boundaries of the panel first.This technique, called banding, allows the painter to maintain adequate coverageat the edges of the panel without extending the spray stroke well beyond the endof the panel surface (Figure 9).

When applying a topcoat, use hiding power labels to determine when thesurface has been adequately covered. Through the use of these labels, thetechnician can be assured of achieving proper coverage without the application ofexcess material (Figure 10).

T he proper cleaning andmaintenance of spray equipment

has always been an essential part ofachieving a quality finish. This isespecially true with newer hightransfer efficiency spraytechnologies. These new spray gunsare machined to very close tolerancesand are highly susceptible to driedpaint or other obstructions that canaffect the performance of the gun.The EPA has estimated that 20percent of all VOC emissionsreleased by automobile refinishersoccur during cleanup operations(Figure 11).

A . Manual Cleaning ProcessesPrior to the introduction of paint

gun cleaning systems, all sprayequipment was cleaned by handusing the following basic steps:

• Remove all remaining paint from the cup.

• With the air hose and cup removed, pull the gun trigger to remove all remaining paint from the siphon tube.

• Rinse the cup with a small amountof thinner.

• Pour clean thinner into the cup and reattach it to the gun.

• With the air supply reattached,spray the thinner through the gunto remove any paint remaining in the interior orifices.

• Remove the cup and pour thinner out of the cup.

• Wipe off the outside of the gun,and inside and outside of the cup using a rag or paper towel.

• Remove the air cap and clean with a cleaning brush. A cleaning brush is also used to clean other external moving parts and behind

the trigger.

• Reassemble the gun and return it to its storage area.Many painters remove the air cap from the gun and place it in the cup.A small amount of thinner is left in the cup so the cap can soak during storage.

Using metal objects to clean thesmall passageways can result insevere damage which greatly reducesthe efficiency of the spray gun. Ifn e e d e d , use a soft wooden toothpick toremove obstructions from the orifices.

These manual cleaning tech n i q u e s,still commonly used in many smallshops, release an excessive amountof VOCs to the atmosphere. They


5. Spray EquipmentCleaning

Figure 11: EPA Estimates of VOC

TopcoatsEquipment Cleaning (20%)


20% of VOCemissions are releasedduring gun cleaningoperations

T he proper cleaning andmaintenance of spray equipment

has always been an essential part ofachieving a quality finish. This isespecially true with newer hightransfer efficiency spraytechnologies. These new spray gunsare machined to very close tolerancesand are highly susceptible to driedpaint or other obstructions that canaffect the performance of the gun.The EPA has estimated that 20percent of all VOC emissionsreleased by automobile refinishersoccur during cleanup operations(Figure 11).

A . Manual Cleaning ProcessesPrior to the introduction of paint

gun cleaning systems, all sprayequipment was cleaned by handusing the following basic steps:

• Remove all remaining paint from the cup.

• With the air hose and cup removed, pull the gun trigger to remove all remaining paint from the siphon tube.


• Pour clean thinner into the cup and reattach it to the gun.

• With the air supply reattached,spray the thinner through the gunto remove any paint remaining in the interior orifices.

• Remove the cup and pour thinner out of the cup.

• Wipe off the outside of the gun,and inside and outside of the cup using a rag or paper towel.

• Remove the air cap and clean with a cleaning brush. A cleaning brush is also used to clean other external moving parts and behind

the trigger.

• Reassemble the gun and return it to its storage area.Many painters remove the air cap from the gun and place it in the cup.A small amount of thinner is left in the cup so the cap can soak during storage.

Using metal objects to clean thesmall passageways can result insevere damage which greatly reducesthe efficiency of the spray gun. Ifn e e d e d , use a soft wooden toothpick toremove obstructions from the orifices.

These manual cleaning tech n i q u e s,still commonly used in many smallshops, release an excessive amountof VOCs to the atmosphere. They


5. Spray EquipmentCleaning


TopcoatsEquipment Cleaning (20%)


20% of VOCemissions are releasedduring gun cleaningoperations

5: Spray Equipment Cleaning


Figure 13: A Two Gun Capacity Gun Wash System

C. Recommended Practices for Spray Equipment Cleaning•Use an air powered mechanical gun cleaning system.

•Use low VOC cleaning solvents.

•If cleaning guns manually, spray into an enclosed backdrop to capture atomized solvents.

•Never use metal objects to remove dried paint or other obstructions from the small orifices of spray equipment. If necessary, use a soft wooden toothpick.



also expose the operator to solventsfor an extended amount of time.

B. Pneumatically PoweredMechanical Cleaning Systems

Within the last few years themechanical gun wash system hasgained popularity in the refinishingindustry. Mechanical gun washers(Figure 12) provide a safe, quick wayto effectively clean paint equipment,including HVLP and LPLV sprayguns. The initial cleaning steps usedwith mechanical gun cleaners arethe same as cleaning a gun usingmanual techniques.

• Remove all the remaining paint from the cup.

• With the air hose removed, pull the trigger of the gun to remove all remaining paint from the siphon tube.


Following these initial cleaningsteps, the disassembled gun is then

placed in the gun washer. The gun'ssiphon tube is placed in the siphontube holder, and the gun trigger islocked open using a locking plate.The cup is simply inverted andplaced over a cleaning jet. The lid ofthe washer is then closed and thewasher turned on. The operator canleave the cleaning station andremain away from paint, thinner,and isocyanate fumes. After 1 - 3minutes, the painter can remove thecleaned spray gun from the washer.The washer lid must then be closedto prevent the thinner fromevaporating and to keep the VOCemissions to a minimum.

With proper use and maintenance,these units reduce the amount ofthinner used during the cleaningprocess by more than one-half (somemanufacturers boast a 75 - 90percent reduction). Mechanicalsystems also reduce the labor timeneeded for equipment cleaning byover 60 percent.

Although VOC emissions from gunwashing systems (Figure 13) haveyet to be accurately measured, thereduction should be substantial. Inaddition, some solvent manufac-turers offer a low VOC gun washsolvent to further reduce emissionsfrom cleaning operations.

Figure 12: Enclosed Air Powered Mechanical Cleaning System

Mechanical cleaningsystems reduce theamount of thinner

used during thecleaning process bymore than one half



Figure 13: A Two Gun Capacity Gun Wash System

C. Recommended Practices for Spray Equipment Cleaning•Use an air powered mechanical gun cleaning system.


•If cleaning guns manually, spray into an enclosed backdrop to capture atomized solvents.

•Never use metal objects to remove dried paint or other obstructions from the small orifices of spray equipment. If necessary, use a soft wooden toothpick.



also expose the operator to solventsfor an extended amount of time.

B. Pneumatically PoweredMechanical Cleaning Systems

Within the last few years themechanical gun wash system hasgained popularity in the refinishingindustry. Mechanical gun washers(Figure 12) provide a safe, quick wayto effectively clean paint equipment,including HVLP and LPLV sprayguns. The initial cleaning steps usedwith mechanical gun cleaners arethe same as cleaning a gun usingmanual techniques.

• Remove all the remaining paint from the cup.

• With the air hose removed, pull the trigger of the gun to remove all remaining paint from the siphon tube.


Following these initial cleaningsteps, the disassembled gun is then

placed in the gun washer. The gun'ssiphon tube is placed in the siphontube holder, and the gun trigger islocked open using a locking plate.The cup is simply inverted andplaced over a cleaning jet. The lid ofthe washer is then closed and thewasher turned on. The operator canleave the cleaning station andremain away from paint, thinner,and isocyanate fumes. After 1 - 3minutes, the painter can remove thecleaned spray gun from the washer.The washer lid must then be closedto prevent the thinner fromevaporating and to keep the VOCemissions to a minimum.

With proper use and maintenance,these units reduce the amount ofthinner used during the cleaningprocess by more than one-half (somemanufacturers boast a 75 - 90percent reduction). Mechanicalsystems also reduce the labor timeneeded for equipment cleaning byover 60 percent.

Although VOC emissions from gunwashing systems (Figure 13) haveyet to be accurately measured, thereduction should be substantial. Inaddition, some solvent manufac-turers offer a low VOC gun washsolvent to further reduce emissionsfrom cleaning operations.

Figure 12: Enclosed Air Powered Mechanical Cleaning System

Mechanical cleaningsystems reduce theamount of thinner

used during thecleaning process bymore than one half

T he VOC content of paints orrelated products may be found on

the Material Safety Data Sheet(MSDS) provided by themanufacturer. The MSDS lists theVOC content of the product asshipped in pounds per gallon, minuswater and non-VOC solvents (Figure 14).

The listed VOC content gives theuser a means of comparing differentproducts. Use caution whencomparing these values because thelisted VOC content is of the productas packaged, not necessarily itssprayable form. Most productsrequire the addition of reducers,thinners,hardeners orr e a c t o r sp r i o r toapplication.Theseadditivescontain up to100 percentVOCs byvolume andwill change the VOCcontent ofthe coating.For example,if a topcoat isto be mixedwith ahardener andreducer at aratio of 2:1:1

respectively, then the VOC contentshould be calculated as follows.

This sprayable product has a VOCcontent of 5.75 lbs/gal, not 4.50lbs/gal as listed on its MSDS.

When comparing product VOCcontent, the amount of the productneeded should also be considered. Ifa product has a low VOC content butrequires 3 - 4 applications, it mayactually release a greater volume ofVOCs during the operation than ahigh VOC product that will performequally well using two light coats.


6. Determining ProductVOC Content

Paint VOC content - 4.50 lbs/gal x 50% = 2.25 Hardener VOC content - 6.44 lbs/gal x 25% = 1.61 Reducer VOC content - 7.55 lbs/gal x 25% = 1.89

100% = 5.75 lbs/gal

Figure 14: Determining VOC Content from the Material Safety Data Sheet

MSDS sheets list the VOC content aspackaged










100% = 5.75 lbs/gal












100% = 5.75 lbs/gal



T o achieve maximum adhesionbetween the surface to be

refinished (the substrate) and theundercoat, the surface must first becleansed of all contamination.Cleaners are used to remove dirt,grease, wax, silicon, mold releaseagents (used in plastic and rubberproduction) and any other contam-inants that could compromise theundercoat's adhesion to the substrate.Many of these cleaners containtoluene, which is listed as both aVOC and a HAP. The EPA hasestimated that 8 percent of all VOCsreleased during the refinishingprocess result from surface prepoperations (Figure 15).

A. Soap and WaterPrior to working on an automobile,

all dirt should be removed from thesurface. To limit the amount ofsolvent used for surface prep, use amild detergent or car wash soap toclean off road grime and dirt. Thenrinse the surface with water toremove any remaining soap. This isone of the simplest and leastexpensive means of reducing bothVOC emissions and material costs.This process also flushes the dirt anddust from body seams, reducing therisk of dirt blowback duringrefinishing. Biodegradabledetergents do not generate any VOCemissions.

B. Synthetic ReducersIn the past, some painters have

used reducers as a pre-paint cleaner.Reducers were popular mainly

because they eliminated the need forthe purchase of a second, lessversatile product. But reducers haveproved to be unsatisfactory pre-paintcleaners for several reasons. R e d u c e r sdo not remove silicone from surfacesas efficiently as commerciallyproduced cleaners and they have atendency to soften existing paintsand primers, causing them to swelland blister. In addition, syntheticreducers are 100 percent VOCs.

C. Solvent-Based CleanersAfter all the road dirt and grime

have been removed, a solvent-basedcleaner can be used to effectivelyremove all grease, wax and siliconefrom the surface. Solvent-basedcleaners typically have a VOCcontent of 6.0 lbs/gal and maycontain up to 100 percent solvent.

Most prep cleaners come in twoformulas and strengths. One type isused for the initial surface cleaningprior to sanding. They are designedto remove heavy silicone, wax andgrease contamination. Many of thesecleaners contain harsh solvents such


7. Surface Prep


To limit the amountof solvents used, amild detergent shouldbe used to remove roadgrime and dirt.


Surface Prep (8%)Under Coats (17%)

U ndercoats are defined as allmaterial applied over the

substrate prior to the application ofa topcoat. These primers fall intofour separate categories:

• Prep Coats • Primer-surfacers• Primer-sealers• Sealers

The EPA has estimated thatundercoating processes account for17 percent of all VOCs released duringrefinishing operations (Figure 16).

A. Prep CoatsThe prep coat is applied directly

over bare metal or metal alloy,galvanized or plated metal, plastic orrubber substrates. The type of prepcoat used will vary depending on thesubstrate and the type of coating tobe applied over the prep coat. It isimportant to read and follow alldirections for these products verycarefully and contact your factory

representative with any questionsprior to application. It is alsoadvisable to use one brand of productthroughout the surface coatingoperation while following all factoryrecommendations. This will helptake the guess-work out ofdetermining which products arecompatible. It will also cut downproduct inventory and product wastewithin the shop.

The prep coat has two majorfunctions:

1. Provide a corrosion resistantcoating.

2. Provide maximum adhesionbetween the substrateand the next coatingto be applied.

Metal Conditioners/Conversion Coatings

Metal conditionersare acidic solutionsthat clean the surfaceof the substrate,removing contam-inants that wouldotherwise compromisethe bond between the

substrate and the undercoat. T h emetal conditioner is generally wipedon with a rag, and after 2-4 minutesneutralized with water. Metalconditioners work well only if thesurface has been wiped completelydry after the neutralization processhas been completed. If moistureremains on the metal surface and isallowed to air dry, the integrity ofthe bond between the substrate andthe primer-surfacer will becompromised. The remainingmoisture may also cause oxidation toform on the bare metal surface.


8. Undercoats


Topcoats (55%)

Surface Prep (8%)

EquipmentCleaning (20%)

Undercoats (17%)

Use one brand ofproduct, followingall factoryrecommendations

7: Surface Prep


as xylene and mineral spirits. Thesehighly concentrated solvents, if usedas a final wash, can cause pooradhesion and/or "solvent popping" ofthe topcoat.

The second formula is designed forthe removal of light contaminationand is used primarily for finalcleaning prior to painting. Thesefinal cleaners will not soften thepainted or primed surface like someof the harsher solvents, nor do theyleave harmful residues on thesubstrate.

D. Waterborne CleanersRecently, waterborne cleaners

have been developed to replace thehigh VOC solvent-based cleaners.Like their solvent-basedcounterparts, waterborne cleaners

generally come in two concen-trations. One for the generalcleaning of surfaces, and another forthe final preparation of surfacesprior to painting.

Waterborne cleaners remove wax,grease and silicone like their solvent-based counterparts, but with lessthan one-sixth the VOC content.However, waterborne cleaners dohave three distinct disadvantages.First, they may not remove heavysilicon and grease contamination aswell as traditional solvent-basedcleaners. Second, they do notevaporate as quickly as solvent-based cleaners, thus increasing thetime needed for surface prep.Finally, many of these cleaners arenot recommended for specificsubstrates, such as water-based oracrylic lacquer finishes.

E. Recommended Practices for Surface PrepTo reduce the VOCs emitted during surface prep operations, the following

practices should be implemented:

•Always wash dirt and grime from the vehicle using water or a soap and water mixture.

•Use waterborne cleaners when possible.

•If, due to heavy contamination, waterborne cleaners prove unsatisfactory,use solvent-based cleaners for the initial cleaning of the surface. For secondary cleaning operations, use the waterborne products.

•If waterborne cleaners prove unsatisfactory due to substrate make-up,use solvent-based cleaners sparingly.

•Keep solvent-laden dirty rags in a closed container.•Keep solvent containers closed when not in use.

•If possible, avoid operations that would necessitate multiple prepaint cleaning operations (e.g., post surface prep repair operations which could contaminate the substrate with grease or oil).

Waterborne cleanershave been developed

to replace high VOCcleaners

U ndercoats are defined as allmaterial applied over the

substrate prior to the application ofa topcoat. These primers fall intofour separate categories:

• Prep Coats • Primer-surfacers• Primer-sealers• Sealers

The EPA has estimated thatundercoating processes account for17 percent of all VOCs released duringrefinishing operations (Figure 16).

A. Prep CoatsThe prep coat is applied directly

over bare metal or metal alloy,galvanized or plated metal, plastic orrubber substrates. The type of prepcoat used will vary depending on thesubstrate and the type of coating tobe applied over the prep coat. It isimportant to read and follow alldirections for these products verycarefully and contact your factory

representative with any questionsprior to application. It is alsoadvisable to use one brand of productthroughout the surface coatingoperation while following all factoryrecommendations. This will helptake the guess-work out ofdetermining which products arecompatible. It will also cut downproduct inventory and product wastewithin the shop.

The prep coat has two majorfunctions:

1. Provide a corrosion resistantcoating.

2. Provide maximum adhesionbetween the substrateand the next coatingto be applied.

Metal Conditioners/Conversion Coatings

Metal conditionersare acidic solutionsthat clean the surfaceof the substrate,removing contam-inants that wouldotherwise compromisethe bond between the

substrate and the undercoat. T h emetal conditioner is generally wipedon with a rag, and after 2-4 minutesneutralized with water. Metalconditioners work well only if thesurface has been wiped completelydry after the neutralization processhas been completed. If moistureremains on the metal surface and isallowed to air dry, the integrity ofthe bond between the substrate andthe primer-surfacer will becompromised. The remainingmoisture may also cause oxidation toform on the bare metal surface.


8. Undercoats


Topcoats (55%)

Surface Prep (8%)

EquipmentCleaning (20%)

Undercoats (17%)

Use one brand ofproduct, followingall factoryrecommendations

7: Surface Prep


as xylene and mineral spirits. Thesehighly concentrated solvents, if usedas a final wash, can cause pooradhesion and/or "solvent popping" ofthe topcoat.

The second formula is designed forthe removal of light contaminationand is used primarily for finalcleaning prior to painting. Thesefinal cleaners will not soften thepainted or primed surface like someof the harsher solvents, nor do theyleave harmful residues on thesubstrate.

D. Waterborne CleanersRecently, waterborne cleaners

have been developed to replace thehigh VOC solvent-based cleaners.Like their solvent-basedcounterparts, waterborne cleaners

generally come in two concen-trations. One for the generalcleaning of surfaces, and another forthe final preparation of surfacesprior to painting.

Waterborne cleaners remove wax,grease and silicone like their solvent-based counterparts, but with lessthan one-sixth the VOC content.However, waterborne cleaners dohave three distinct disadvantages.First, they may not remove heavysilicon and grease contamination aswell as traditional solvent-basedcleaners. Second, they do notevaporate as quickly as solvent-based cleaners, thus increasing thetime needed for surface prep.Finally, many of these cleaners arenot recommended for specificsubstrates, such as water-based oracrylic lacquer finishes.

E. Recommended Practices for Surface PrepTo reduce the VOCs emitted during surface prep operations, the following

practices should be implemented:

•Always wash dirt and grime from the vehicle using water or a soap and water mixture.

•Use waterborne cleaners when possible.

•If, due to heavy contamination, waterborne cleaners prove unsatisfactory,use solvent-based cleaners for the initial cleaning of the surface. For secondary cleaning operations, use the waterborne products.

•If waterborne cleaners prove unsatisfactory due to substrate make-up,use solvent-based cleaners sparingly.

•Keep solvent-laden dirty rags in a closed container.•Keep solvent containers closed when not in use.

•If possible, avoid operations that would necessitate multiple prepaint cleaning operations (e.g., post surface prep repair operations which could contaminate the substrate with grease or oil).

Waterborne cleanershave been developed

to replace high VOCcleaners

simple, one step, process. A lightcoat of zinc phosphate is sprayed onthe metal surface and allowed to dryfor 30 to 60 minutes. The zincphosphate etches the substrate anddeposits a phosphate coating on thesurface to provide protection frommoisture. The result is a non-reactive roughened surface that isperfect for the application of aprimer coat and needs no sandingprior to surface coating. Theseprimers can be used on both steeland aluminum surfaces. Zincphosphate does not have a pot-life,but must be stirred before each usedue to excessive settling.

Zinc phosphate has a VOC concen-tration of 4.5 - 5.0 lbs/gal aspackaged. The VOC content of thesprayable solution, reduced 1:1 withenamel reducer, is as high as 6.0lbs/gal.

In addition to the high VOC level,zinc phosphate has four otherdistinct disadvantages.

1. It is not recommended for use as aprimer under many waterborne primer-surfacers.

2. Zinc phosphate does not adhere aswell as the wash-primers or self-etching primers.

3. The primer has no filling capabilities.

4. The 30 - 60 minute curing time of the zinc phosphate may be unsatisfactory for production surface coating operations.

Self-Etching Primers

Self-etching primers are usuallytwo component primers that providegood corrosion resistance and good

adhesion to bare metal substrates.These primers also have some fillingproperties to hide minor surfaceimperfections. The primed surfacemay be sanded and recoated usuallyafter 45 - 60 minutes.

The VOC content of self etchingprimers ranges from 5.0 - 6.5 lbs/galas packaged. With the addition ofthe activator and reducer, the totalVOC content of the sprayableproduct may be as high as 6.0 - 7.0lbs/gal. In addition to the high VOCcontent, these coatings also have thedisadvantage of a pot-life rangingfrom several hours to several daysdepending on the product.

Epoxy Primers

Epoxy primers are one of the mostversatile automotive paint productson the market today. These twocomponent primers can be used as aprimer, primer-surfacer, primer-sealer, and adhesion promoter.Epoxy primers provide excellentcorrosion resistance and adhesion tobare metal and coated surfaces. Theepoxy resins in the primer produce astrong chip resistant surface over thesubstrate.

Solvent-based self-etching epoxyprimers have a VOC content ofapproximately 3.5 - 4.0 lbs/gal. Withthe addition of the activator andreducer, the sprayable primers haveVOC contents of approximately 5.0lbs/gal.

These products also have a pot-life,some as little as 6-8 hours, whichmay increase the amount of wastematerial generated. The curing timefor these primers ranges from 1 to 2hours for the solvent-based, to asmuch as 10 hours for the waterborne

8: Undercoats


Epoxy primers areone of the mostversatile products onthe market

8: Undercoats


Following the metal conditioner, aconversion coating is applied to thesubstrate. This conversion coating,usually phosphoric acid, etches themetal to improve bonding with theprimer-surfacer. The conversioncoating also leaves a phosphatecoating on the surface of thesubstrate, forming a more corrosion-resistant surface.

Although this system contains lowamounts of VOCs (approximately 1.0lbs/gal) it has some distinctdisadvantages. First, the primer-surfacer must be sprayed on shortlyafter the metal conditioning processhas been completed to avoidcorrosion of the metal. Second, theemployee performing the metalconditioning operation is exposed toan acidic solution which may causeskin irritation. Finally, the metalconditioner-conversion coatingsystem is time consuming, especiallywhen large areas require treatment.

Wash-Primers/Vinyl Wash-Primers

Wash-primers were developed toeliminate one of the steps associatedwith metal conditioner andconversion coating systems. Wash-primers contain either phosphoricacid or nickel dihydrogen phosphate,which forms an adherent phosphatecoating when applied to steel andaluminum. The acid also removesrust, welding scale, and oil from thebare metal while etching the surfaceto insure the good adhesion of theprimer-surfacer.

Wash-primers are usually sprayedon the metal surface using a handheld plastic sprayer. Many washprimers must be neutralized with

water and dried prior to surfacecoating. Most of these conditionersare low in VOCs, with averagecontents of approximately 1.0 lb/gal.Some of the newer water basedwash-primers do not contain VOCs.

Application of these productsrequires caution. Some are designedfor use on steel surfaces only, andshould not be used on aluminumsubstrates. Application to anysurface other then a bare metalsurface must also be avoided, aslifting of the surface coat may result.

Some wash-primers are designedfor use on most metal surfaces aswell as plastic and rubbersubstrates. These wash-primersform a good bond between thetopcoat and the hard-to-adhere-to,plastic and rubber surfaces.

Since wash-primers react withmetal surfaces, the use of a paintgun for application should beavoided. Wash-primers can reactwith the metal spray gun, resultingin an adhesive coating formed insidethe cup and on the interiorcomponents of the gun. For thisreason, the solution should beapplied by hand or with a non-metallic spray bottle. Check withyour paint supplier for specificrecommendations.

Zinc Phosphate Primers

Many automobile manufacturersuse zinc phosphate coatings as aprimer during surface coatingoperations. In the factory, theapplication of the zinc phosphatecoating is a multi-step, timeconsuming process. But zincphosphate systems used as a primerin the refinishing industry are a

Conversion coatingleaves a phosphate

coating on thesubstrate

Some water basedwash-primers

contain no VOCs

simple, one step, process. A lightcoat of zinc phosphate is sprayed onthe metal surface and allowed to dryfor 30 to 60 minutes. The zincphosphate etches the substrate anddeposits a phosphate coating on thesurface to provide protection frommoisture. The result is a non-reactive roughened surface that isperfect for the application of aprimer coat and needs no sandingprior to surface coating. Theseprimers can be used on both steeland aluminum surfaces. Zincphosphate does not have a pot-life,but must be stirred before each usedue to excessive settling.

Zinc phosphate has a VOC concen-tration of 4.5 - 5.0 lbs/gal aspackaged. The VOC content of thesprayable solution, reduced 1:1 withenamel reducer, is as high as 6.0lbs/gal.

In addition to the high VOC level,zinc phosphate has four otherdistinct disadvantages.

1. It is not recommended for use as aprimer under many waterborne primer-surfacers.

2. Zinc phosphate does not adhere aswell as the wash-primers or self-etching primers.

3. The primer has no filling capabilities.

4. The 30 - 60 minute curing time of the zinc phosphate may be unsatisfactory for production surface coating operations.

Self-Etching Primers

Self-etching primers are usuallytwo component primers that providegood corrosion resistance and good

adhesion to bare metal substrates.These primers also have some fillingproperties to hide minor surfaceimperfections. The primed surfacemay be sanded and recoated usuallyafter 45 - 60 minutes.

The VOC content of self etchingprimers ranges from 5.0 - 6.5 lbs/galas packaged. With the addition ofthe activator and reducer, the totalVOC content of the sprayableproduct may be as high as 6.0 - 7.0lbs/gal. In addition to the high VOCcontent, these coatings also have thedisadvantage of a pot-life rangingfrom several hours to several daysdepending on the product.

Epoxy Primers

Epoxy primers are one of the mostversatile automotive paint productson the market today. These twocomponent primers can be used as aprimer, primer-surfacer, primer-sealer, and adhesion promoter.Epoxy primers provide excellentcorrosion resistance and adhesion tobare metal and coated surfaces. Theepoxy resins in the primer produce astrong chip resistant surface over thesubstrate.

Solvent-based self-etching epoxyprimers have a VOC content ofapproximately 3.5 - 4.0 lbs/gal. Withthe addition of the activator andreducer, the sprayable primers haveVOC contents of approximately 5.0lbs/gal.

These products also have a pot-life,some as little as 6-8 hours, whichmay increase the amount of wastematerial generated. The curing timefor these primers ranges from 1 to 2hours for the solvent-based, to asmuch as 10 hours for the waterborne

8: Undercoats


Epoxy primers areone of the mostversatile products onthe market

8: Undercoats


Following the metal conditioner, aconversion coating is applied to thesubstrate. This conversion coating,usually phosphoric acid, etches themetal to improve bonding with theprimer-surfacer. The conversioncoating also leaves a phosphatecoating on the surface of thesubstrate, forming a more corrosion-resistant surface.

Although this system contains lowamounts of VOCs (approximately 1.0lbs/gal) it has some distinctdisadvantages. First, the primer-surfacer must be sprayed on shortlyafter the metal conditioning processhas been completed to avoidcorrosion of the metal. Second, theemployee performing the metalconditioning operation is exposed toan acidic solution which may causeskin irritation. Finally, the metalconditioner-conversion coatingsystem is time consuming, especiallywhen large areas require treatment.

Wash-Primers/Vinyl Wash-Primers

Wash-primers were developed toeliminate one of the steps associatedwith metal conditioner andconversion coating systems. Wash-primers contain either phosphoricacid or nickel dihydrogen phosphate,which forms an adherent phosphatecoating when applied to steel andaluminum. The acid also removesrust, welding scale, and oil from thebare metal while etching the surfaceto insure the good adhesion of theprimer-surfacer.

Wash-primers are usually sprayedon the metal surface using a handheld plastic sprayer. Many washprimers must be neutralized with

water and dried prior to surfacecoating. Most of these conditionersare low in VOCs, with averagecontents of approximately 1.0 lb/gal.Some of the newer water basedwash-primers do not contain VOCs.

Application of these productsrequires caution. Some are designedfor use on steel surfaces only, andshould not be used on aluminumsubstrates. Application to anysurface other then a bare metalsurface must also be avoided, aslifting of the surface coat may result.

Some wash-primers are designedfor use on most metal surfaces aswell as plastic and rubbersubstrates. These wash-primersform a good bond between thetopcoat and the hard-to-adhere-to,plastic and rubber surfaces.

Since wash-primers react withmetal surfaces, the use of a paintgun for application should beavoided. Wash-primers can reactwith the metal spray gun, resultingin an adhesive coating formed insidethe cup and on the interiorcomponents of the gun. For thisreason, the solution should beapplied by hand or with a non-metallic spray bottle. Check withyour paint supplier for specificrecommendations.

Zinc Phosphate Primers

Many automobile manufacturersuse zinc phosphate coatings as aprimer during surface coatingoperations. In the factory, theapplication of the zinc phosphatecoating is a multi-step, timeconsuming process. But zincphosphate systems used as a primerin the refinishing industry are a

Conversion coatingleaves a phosphate

coating on thesubstrate

Some water basedwash-primers

contain no VOCs

When applying primer-surfacers,as with all coatings, it is importantto use a gun specially designed foruse with that type of product. Usinga properly operating primer gunwith the correct fluid tip/air capcombination will help reduceoverspray and reduce the waste oftime and material due to a dry oruneven coating.

Acrylic Lacquer Primer- S u r f a c e r

Acrylic lacquer primer-surfacershave been very popular in auto bodyshops over the years. These primer-surfacers provide an easy sandingsurface that drys quickly (usuallywithin 30 minutes) and has goodfilling capabilities. Acrylic lacquerprimer-surfacers also provide goodcorrosion resistance and excellentholdout characteristics. Lacquerbased primer-surfacers are good forspot repair and small panel jobs.However, using lacquer-basedprimers over deteriorating orsensitive surfaces may result inlifting or accelerated deterioration ofthe old painted substrate. Theseprimers are not generallyrecommended for large jobs due totheir poor durability and lack ofcompatibility with the majority oftoday's topcoat systems.

Acrylic lacquer primers usuallyhave a VOC content ranging from4.5 - 5.0 lbs/gal. When thinned(usually 100 - 125 percent) andready to spray, VOC content isapproximately 5.5 - 6.0 lbs/gal.

Alkyd Synthetic Enamel Primer-Surfacer

Alkyd enamel primer-surfacershave good filling and holdout

properties as well as excellentcorrosion resistant qualities. Theyproduce a flexible, tough, chip-resistant base that is excellent forthe application of a topcoat. Becauseof their enamel base, these primer-surfacers are less likely than theirlacquer-based counterparts toadversely affect sensitive substrates.

Alkyd enamel primer-surfacerscontain 4.0 - 4.5 lbs/gal VOCs aspackaged. When thinned to asprayable concentration, the amountof VOCs increases to 4.5 - 5.0 lbsgal. The one distinct drawback ofalkyd enamel primer-surfacers istheir slow curing time. Theseprimer-surfacers must dry for atleast four hours before sandingoperations can be performed. Forthis reason, alkyd enamel primer-surfacers are not typically used forspot repair operations, but ratherlarge panel surfaces and completepaint jobs.

Self-Etching Primers (as aPrimer-Surfacer)

Self-etching primers are usuallytwo-component primers that providegood corrosion resistance with fairfilling qualities. The primed surfacemay be sanded and recoated after 45- 60 minutes of drying time.

The VOC content of self etchingprimers ranges from 5.0 - 6.5 lbs/galas packaged. With the addition ofthe activator and reducer, the totalVOC content of the sprayableproduct may be as high as 6.0 - 7.0lbs/gal. In addition to high VOCcontent, this product also has thedisadvantage of a pot-life rangingfrom several hours to several daysdepending on the product.

8: Undercoats


A properly operatingprimer gun with correct fluid tip/aircap combination willhelp reduce overspray

8: Undercoats


epoxy primers. It should also benoted that some of these primerscontain lead and chrome, and theiractivators may contain isocyanates.

Adhesion Promoters

Adhesion promoters do not providethe corrosion protection supplied byother prep coats and should not beused over bare metal substrates.However, these products do provideimproved adhesion to plastic andrubber components, as well aspainted surfaces.

The application of adhesionpromoters has become an importantstep in the refinishing process withthe growing popularity of the harder,more durable high tech surfacecoatings. When sprayed over OEMurethane, water-based, or high solidspaints and clears, adhesionpromoters provide improvedadhesion between the substrate andthe topcoat. Adhesion promoterscome ready to spray with a VOCcontent of 6.5 - 7.0 lbs/gal. Theygenerally require a curing time ofapproximately 15 - 30 minutes priorto topcoating.

B. Primer-SurfacersThe best way to limit VOC

emissions during the primer-surfacerstage of the refinishing process is tominimize the number of coatsapplied. By ensuring that all majorbody imperfections are removed priorto priming operations, the techniciannot only reduces the amount ofexpensive material used during therepair process, but also reduces theamount of VOCs released. Primer-surfacers should only be used toremove small imperfections such assanding scratches; they are notmeant to fill dents.

Primer-surfacers are sprayed overprimers and have the followingfunctions:

1. Provide adhesion between the primer and the material to be applied over the primer-surfacer.This includes the primer-sealers,sealers, and topcoats.

2. Provide corrosion protection to themetallic substrate.

3. Act as a filling material to cover minor surface flaws.

4. Provide a coating that can be `easily sanded to a smooth surface.

If a primer-sealer or sealer will notbe used over the primer-surfacer, orif the sealer to be used istransparent, the color of the primer-surfacer must be considered. Toreduce VOC emissions and theamount of paint required, choose aprimer which is a color that caneasily be covered by the topcoat.Some primers on the market todayare tintable, allowing for easycoverage of the surface-primer by thetopcoat. Many primer-surfacers stillcontain lead and chromium. Mosttwo component primer-surfacerscontain isocyanates.

Recommended Practices for PrepCoats

• Use versatile products such as epoxy primers or self-etching p r i m e r s. These products mayalleviate the need for additional surface coating operations suchas primer-surfacing or primer sealing.

• If a self-etching primer or epoxy primer is not desirable, use a wa s h - p r i m e r, or metal conditioner,conversion coating system.

• Avoid high VOC content zinc phosphate primers.

Minimizing thenumber of coats

applied limits theamount of VOCs

emitted during theprimer-surfacer

stage

Primer-surfacersshould be used to fill

small imperfectionsonly

When applying primer-surfacers,as with all coatings, it is importantto use a gun specially designed foruse with that type of product. Usinga properly operating primer gunwith the correct fluid tip/air capcombination will help reduceoverspray and reduce the waste oftime and material due to a dry oruneven coating.

Acrylic Lacquer Primer- S u r f a c e r

Acrylic lacquer primer-surfacershave been very popular in auto bodyshops over the years. These primer-surfacers provide an easy sandingsurface that drys quickly (usuallywithin 30 minutes) and has goodfilling capabilities. Acrylic lacquerprimer-surfacers also provide goodcorrosion resistance and excellentholdout characteristics. Lacquerbased primer-surfacers are good forspot repair and small panel jobs.However, using lacquer-basedprimers over deteriorating orsensitive surfaces may result inlifting or accelerated deterioration ofthe old painted substrate. Theseprimers are not generallyrecommended for large jobs due totheir poor durability and lack ofcompatibility with the majority oftoday's topcoat systems.

Acrylic lacquer primers usuallyhave a VOC content ranging from4.5 - 5.0 lbs/gal. When thinned(usually 100 - 125 percent) andready to spray, VOC content isapproximately 5.5 - 6.0 lbs/gal.

Alkyd Synthetic Enamel Primer-Surfacer

Alkyd enamel primer-surfacershave good filling and holdout

properties as well as excellentcorrosion resistant qualities. Theyproduce a flexible, tough, chip-resistant base that is excellent forthe application of a topcoat. Becauseof their enamel base, these primer-surfacers are less likely than theirlacquer-based counterparts toadversely affect sensitive substrates.

Alkyd enamel primer-surfacerscontain 4.0 - 4.5 lbs/gal VOCs aspackaged. When thinned to asprayable concentration, the amountof VOCs increases to 4.5 - 5.0 lbsgal. The one distinct drawback ofalkyd enamel primer-surfacers istheir slow curing time. Theseprimer-surfacers must dry for atleast four hours before sandingoperations can be performed. Forthis reason, alkyd enamel primer-surfacers are not typically used forspot repair operations, but ratherlarge panel surfaces and completepaint jobs.

Self-Etching Primers (as aPrimer-Surfacer)

Self-etching primers are usuallytwo-component primers that providegood corrosion resistance with fairfilling qualities. The primed surfacemay be sanded and recoated after 45- 60 minutes of drying time.

The VOC content of self etchingprimers ranges from 5.0 - 6.5 lbs/galas packaged. With the addition ofthe activator and reducer, the totalVOC content of the sprayableproduct may be as high as 6.0 - 7.0lbs/gal. In addition to high VOCcontent, this product also has thedisadvantage of a pot-life rangingfrom several hours to several daysdepending on the product.

8: Undercoats


A properly operatingprimer gun with correct fluid tip/aircap combination willhelp reduce overspray

8: Undercoats


epoxy primers. It should also benoted that some of these primerscontain lead and chrome, and theiractivators may contain isocyanates.

Adhesion Promoters

Adhesion promoters do not providethe corrosion protection supplied byother prep coats and should not beused over bare metal substrates.However, these products do provideimproved adhesion to plastic andrubber components, as well aspainted surfaces.

The application of adhesionpromoters has become an importantstep in the refinishing process withthe growing popularity of the harder,more durable high tech surfacecoatings. When sprayed over OEMurethane, water-based, or high solidspaints and clears, adhesionpromoters provide improvedadhesion between the substrate andthe topcoat. Adhesion promoterscome ready to spray with a VOCcontent of 6.5 - 7.0 lbs/gal. Theygenerally require a curing time ofapproximately 15 - 30 minutes priorto topcoating.

B. Primer-SurfacersThe best way to limit VOC

emissions during the primer-surfacerstage of the refinishing process is tominimize the number of coatsapplied. By ensuring that all majorbody imperfections are removed priorto priming operations, the techniciannot only reduces the amount ofexpensive material used during therepair process, but also reduces theamount of VOCs released. Primer-surfacers should only be used toremove small imperfections such assanding scratches; they are notmeant to fill dents.

Primer-surfacers are sprayed overprimers and have the followingfunctions:

1. Provide adhesion between the primer and the material to be applied over the primer-surfacer.This includes the primer-sealers,sealers, and topcoats.

2. Provide corrosion protection to themetallic substrate.

3. Act as a filling material to cover minor surface flaws.

4. Provide a coating that can be `easily sanded to a smooth surface.

If a primer-sealer or sealer will notbe used over the primer-surfacer, orif the sealer to be used istransparent, the color of the primer-surfacer must be considered. Toreduce VOC emissions and theamount of paint required, choose aprimer which is a color that caneasily be covered by the topcoat.Some primers on the market todayare tintable, allowing for easycoverage of the surface-primer by thetopcoat. Many primer-surfacers stillcontain lead and chromium. Mosttwo component primer-surfacerscontain isocyanates.

Recommended Practices for PrepCoats

• Use versatile products such as epoxy primers or self-etching p r i m e r s. These products mayalleviate the need for additional surface coating operations suchas primer-surfacing or primer sealing.

• If a self-etching primer or epoxy primer is not desirable, use a wa s h - p r i m e r, or metal conditioner,conversion coating system.


Minimizing thenumber of coats

applied limits theamount of VOCs

emitted during theprimer-surfacer

stage

Primer-surfacersshould be used to fill

small imperfectionsonly

C. Primer-SealersPrimer-sealers differ from primer-

surfacers in two basic areas. First,primer sealers fill only very minorimperfections. Second, they shouldnot be sanded prior to theapplication of a topcoat.

Primer-sealers must meet thefollowing performance criteria:

1. Provide corrosion resistance.2. Provide adhesion to bare metal

substrate.3. Fill minor surface imperfections.4. Seal sanded surfaces to prevent

solvent penetration and bleed-through.

5. Provide a single, neutral-colored base for easy topcoat coverage.

The choice of sealer color affectsnot only the coverage of the topcoats,but may also affect the final color

shade of the finish, especially whenusing topcoats containingtransparent pigments. The primer-sealer should be as close to the colorof the factory sealer as possible.

Lacquer Primer-Sealers

Lacquer primer-sealers producefair filling qualities with goodadhesion properties. These primersare designed to be topcoated withlacquer topcoats. One coat is

generally recommended prior topainting with a 30 minute dryingtime.

Lacquer primer-sealers arecommonly used for spot repair andsmall paint jobs, but not generallyfor large surface coating operations.VOC content is approximately 6.0lbs/gal as packaged in sprayable form.

Enamel Type Primer-Sealers

Enamel type primer-sealers alsohave fair filling qualities with goodadhesion and holdout properties.Usually used for large panel or

8: Undercoats


Recommended Practices forPrimer-Surfacers

• Use low VOC waterborne primer-surfacer products.

• If the curing time of waterborne products is unsatisfactory,consider the use of versatile urethane or epoxy primers.

• To reduce VOC emissions, limit material costs, and achieve a better quality product, make sure body work is done in such a manner as to require only a minimal amount of primer-surfacer.

• If a colored sealer will not be used,make sure the primer-surfacer used is a color that can easily be covered with the desired topcoat.

• Use a properly operating primer gun with the correct fluid tip/air cap combination for your particulartype of primer-surfacer.

Figure 17: Application of the Primer-Sealer

The choice of sealercolor affects not onlythe coverage of thetopcoats but mayalso affect the finalcolor shade of thefinish

8: Undercoats


One-Component WaterbornePrimer-Surfacer

When waterborne primers wereintroduced to the collision repairmarket in the mid-to-late 1980's,they were met with controversy andresistance. Waterborne primers havebeen reported to cause rusting ofuntreated metallic substrates andnon-coated ferrous spray equipmentcomponents. Some painters feelthese products have a curing timetoo slow for production work,especially in regions with highhumidity. While many of thesereported problems are due toimproper use of the product, longcuring times remain the primers’greatest adversary.

These primers do have some verybeneficial qualities. They possessexcellent high building propertieswith tremendous hold-outcapabilities. Many can be used onflexible parts as a primer withoutthe need for the addition of a flexagent. Single component waterborneprimers come ready to spray with a4.5 - 5.0 lbs/gal VOC content,resulting in a 20 percent reduction inVOC emissions as compared toconventional solvent- based primers.

Epoxy Primer (as a Primer-Surfacer)

As a primer-surfacer, epoxyprimers provide excellent fillingqualities and possess excellent hold-out capabilities. The tough surfaceproduced by the epoxies makes agood durable base for the applicationof any topcoat.

Solvent-based self-etching epoxyprimers have a VOC content ofapproximately 3.5 - 4.0 lbs/gal. With

the addition of the activator andreducer, the sprayable primer-surfacer formula has a VOC contentof up to 4.5 lbs/gal. Waterborneepoxy primers, which are alsoavailable, have a VOC content of lessthen 2.1 lbs/gal for the sprayableproduct.

Polyester Primer-Surfacer

Polyester primer-surfacers containpolyester resins which, when cured,form a durable surface with excellenthigh building qualities and minimalshrinkage. Because of their highviscosity, polyester primer-surfacersare best sprayed using gravity feedspray equipment.

Polyester primer-surfacers have arelatively long curing time, rangingfrom 2 - 3 hours. These primer-surfacers generally do not sand aseasily as other primer-surfacers, andsome loss in productivity may result.The topcoats that can be applied tothese primer-surfacers are usuallylimited to the newer polyurethanes.The VOC content of polyesterprimer-surfacers ranges from 4.6 to5.0 lbs/gal thinned and ready tospray.

Acrylic Urethane Enamel Primer-Surfacer

Acrylic urethane was developed forthe newer high tech topcoats. Theseprimer-surfacers provide high buildcharacteristics with little or noshrinkage. Urethane primer-surfacers have a VOC contentranging from 4.3 - 5.0 lbs/gal afterthe addition of the activator andreducer. Urethane primer-surfacershave a relatively slow curing time,some requiring up to two hours tocure under ideal conditions.

Single componentwaterborne primers

come ready to spraywith a 4.5 - 5.0

lbs/gal VOC content

C. Primer-SealersPrimer-sealers differ from primer-

surfacers in two basic areas. First,primer sealers fill only very minorimperfections. Second, they shouldnot be sanded prior to theapplication of a topcoat.

Primer-sealers must meet thefollowing performance criteria:

1. Provide corrosion resistance.2. Provide adhesion to bare metal

substrate.3. Fill minor surface imperfections.4. Seal sanded surfaces to prevent

solvent penetration and bleed-through.

5. Provide a single, neutral-colored base for easy topcoat coverage.

The choice of sealer color affectsnot only the coverage of the topcoats,but may also affect the final color

shade of the finish, especially whenusing topcoats containingtransparent pigments. The primer-sealer should be as close to the colorof the factory sealer as possible.

Lacquer Primer-Sealers

Lacquer primer-sealers producefair filling qualities with goodadhesion properties. These primersare designed to be topcoated withlacquer topcoats. One coat is

generally recommended prior topainting with a 30 minute dryingtime.

Lacquer primer-sealers arecommonly used for spot repair andsmall paint jobs, but not generallyfor large surface coating operations.VOC content is approximately 6.0lbs/gal as packaged in sprayable form.

Enamel Type Primer-Sealers

Enamel type primer-sealers alsohave fair filling qualities with goodadhesion and holdout properties.Usually used for large panel or

8: Undercoats


Recommended Practices forPrimer-Surfacers

• Use low VOC waterborne primer-surfacer products.

• If the curing time of waterborne products is unsatisfactory,consider the use of versatile urethane or epoxy primers.


• If a colored sealer will not be used,make sure the primer-surfacer used is a color that can easily be covered with the desired topcoat.

• Use a properly operating primer gun with the correct fluid tip/air cap combination for your particulartype of primer-surfacer.

Figure 17: Application of the Primer-Sealer

The choice of sealercolor affects not onlythe coverage of thetopcoats but mayalso affect the finalcolor shade of thefinish

8: Undercoats


One-Component WaterbornePrimer-Surfacer

When waterborne primers wereintroduced to the collision repairmarket in the mid-to-late 1980's,they were met with controversy andresistance. Waterborne primers havebeen reported to cause rusting ofuntreated metallic substrates andnon-coated ferrous spray equipmentcomponents. Some painters feelthese products have a curing timetoo slow for production work,especially in regions with highhumidity. While many of thesereported problems are due toimproper use of the product, longcuring times remain the primers’greatest adversary.

These primers do have some verybeneficial qualities. They possessexcellent high building propertieswith tremendous hold-outcapabilities. Many can be used onflexible parts as a primer withoutthe need for the addition of a flexagent. Single component waterborneprimers come ready to spray with a4.5 - 5.0 lbs/gal VOC content,resulting in a 20 percent reduction inVOC emissions as compared toconventional solvent- based primers.

Epoxy Primer (as a Primer-Surfacer)

As a primer-surfacer, epoxyprimers provide excellent fillingqualities and possess excellent hold-out capabilities. The tough surfaceproduced by the epoxies makes agood durable base for the applicationof any topcoat.

Solvent-based self-etching epoxyprimers have a VOC content ofapproximately 3.5 - 4.0 lbs/gal. With

the addition of the activator andreducer, the sprayable primer-surfacer formula has a VOC contentof up to 4.5 lbs/gal. Waterborneepoxy primers, which are alsoavailable, have a VOC content of lessthen 2.1 lbs/gal for the sprayableproduct.

Polyester Primer-Surfacer

Polyester primer-surfacers containpolyester resins which, when cured,form a durable surface with excellenthigh building qualities and minimalshrinkage. Because of their highviscosity, polyester primer-surfacersare best sprayed using gravity feedspray equipment.

Polyester primer-surfacers have arelatively long curing time, rangingfrom 2 - 3 hours. These primer-surfacers generally do not sand aseasily as other primer-surfacers, andsome loss in productivity may result.The topcoats that can be applied tothese primer-surfacers are usuallylimited to the newer polyurethanes.The VOC content of polyesterprimer-surfacers ranges from 4.6 to5.0 lbs/gal thinned and ready tospray.

Acrylic Urethane Enamel Primer-Surfacer

Acrylic urethane was developed forthe newer high tech topcoats. Theseprimer-surfacers provide high buildcharacteristics with little or noshrinkage. Urethane primer-surfacers have a VOC contentranging from 4.3 - 5.0 lbs/gal afterthe addition of the activator andreducer. Urethane primer-surfacershave a relatively slow curing time,some requiring up to two hours tocure under ideal conditions.

Single componentwaterborne primers

come ready to spraywith a 4.5 - 5.0

lbs/gal VOC content

In general, sealer types includelacquer sealers, enamel sealers, andurethane sealers. These sealers aredeveloped to be coated by lacquer,enamel and urethane topcoatsrespectively, and generally requireonly one coat prior to painting.These sealers come ready to spraywith VOC contents of approximately6.5, 6.0, 6.0 lbs/gal respectively.

As with primer-sealers, the choiceof sealer color affects coverage andthe final shade of your topcoat,especially topcoats containingtransparent pigments. Therefore,when choosing a sealer, always takeinto account the sealer color as wellas the topcoating.

Along with these basic sealers,there are also specialty sealersavailable for use on specific problemsurfaces.

Tie Coat Sealers

Tie coat sealers are used toachieve extra adhesion betweenlacquer topcoats and factory enamelfinishes.

Barrier Coat Sealers

Barrier coat sealers are appliedover very sensitive and or checkedsurfaces. These sealers supplysuperb holdout, preventing thelifting or checking of the newtopcoat.

8: Undercoats


Recommended Practices forSealers

• Chose the proper sealer for eachspecific job.

• If filling capabilities are required,use primer-sealer in place of a sealer.

• Always choose a primer-sealer color that can be easily covered with the next coating, or choose a tintable primer-sealer.

When choosing asealer, take intoaccount the color ofthe sealer as well asthe topcoating to beapplied

8: Undercoats


complete paint jobs, only one coat ofprimer-sealer is generally neededprior to topcoating. VOC contentaverages 4.5 - 5.0 lbs/gal.

Single Component WaterbornePrimer-Surfacer (as a Primer-Sealer)

Single component water-basedprimers possess excellent highbuilding qualities and work well asbarrier coats with tremendous hold-out properties. Many can be used onflexible parts as a primer without theaddition of a flex agent.

These primers come ready-to-spraywith a 4.5 - 5.0 lbs/gal VOC content.Because water is used as the primarysolvent, the flash and cure times ofthese products are relatively long,especially in regions of highhumidity. The water may also causethe corrosion of non-coated ferrousapplication equipment if not cleanedproperly.

Epoxy Primer (as a Primer-Sealer)

As a primer-sealer, epoxy primersprovide excellent hold outcapabilities. The tough surfaceproduced by the epoxies makes agood durable base for the applicationof all topcoats.

Solvent-based self-etching epoxyprimers have a VOC content ofapproximately 3.5 - 4.0 lbs/gal. Withthe addition of the activator andr e d u c e r, the sprayable primer- s u r f a c e rformula has a VOC content of 4.5lbs/gal. Waterborne epoxy primershave a VOC content of less then 2.1lbs/gal for the sprayable product.Acrylic Urethane Primer-Sealers

Urethane primer-sealers providehigh build characteristics with littleor no shrinkage. They also havesuperior holdout properties whichmake them an excellent primer-sealer.

Urethane primer-sealers have aVOC content ranging from 4.3 - 5.0lbs/gal after the addition of theactivator and reducers. Urethanesmust usually be topcoated within 24hours to avoid the need for sandingand recoating.

D. Sealers

Sealers are applied prior to thetopcoat if needed. They should havethe following qualities:

1. Provide adhesion between the topcoat and the surface.

2. Provide a single, neutral-colored base for easy coverage.

3. Seal sanded surfaces to prevent solvent penetration.

4. Fill minor imperfections.

Recommended Practices forPrimer-Sealers

• Use low VOC primer-sealers suchas single component waterborne,or waterborne epoxy primers.

• The use of low VOC urethane primer-sealers would also be an acceptable choice.

• Always choose primer-sealer color that can be easily covered by the topcoat to be sprayed, or choose a tintable primer-sealer and tint it toan easily covered shade.

In general, sealer types includelacquer sealers, enamel sealers, andurethane sealers. These sealers aredeveloped to be coated by lacquer,enamel and urethane topcoatsrespectively, and generally requireonly one coat prior to painting.These sealers come ready to spraywith VOC contents of approximately6.5, 6.0, 6.0 lbs/gal respectively.

As with primer-sealers, the choiceof sealer color affects coverage andthe final shade of your topcoat,especially topcoats containingtransparent pigments. Therefore,when choosing a sealer, always takeinto account the sealer color as wellas the topcoating.

Along with these basic sealers,there are also specialty sealersavailable for use on specific problemsurfaces.

Tie Coat Sealers

Tie coat sealers are used toachieve extra adhesion betweenlacquer topcoats and factory enamelfinishes.

Barrier Coat Sealers

Barrier coat sealers are appliedover very sensitive and or checkedsurfaces. These sealers supplysuperb holdout, preventing thelifting or checking of the newtopcoat.

8: Undercoats


Recommended Practices forSealers

• Chose the proper sealer for eachspecific job.

• If filling capabilities are required,use primer-sealer in place of a sealer.

• Always choose a primer-sealer color that can be easily covered with the next coating, or choose a tintable primer-sealer.

When choosing asealer, take intoaccount the color ofthe sealer as well asthe topcoating to beapplied

8: Undercoats


complete paint jobs, only one coat ofprimer-sealer is generally neededprior to topcoating. VOC contentaverages 4.5 - 5.0 lbs/gal.

Single Component WaterbornePrimer-Surfacer (as a Primer-Sealer)

Single component water-basedprimers possess excellent highbuilding qualities and work well asbarrier coats with tremendous hold-out properties. Many can be used onflexible parts as a primer without theaddition of a flex agent.

These primers come ready-to-spraywith a 4.5 - 5.0 lbs/gal VOC content.Because water is used as the primarysolvent, the flash and cure times ofthese products are relatively long,especially in regions of highhumidity. The water may also causethe corrosion of non-coated ferrousapplication equipment if not cleanedproperly.

Epoxy Primer (as a Primer-Sealer)

As a primer-sealer, epoxy primersprovide excellent hold outcapabilities. The tough surfaceproduced by the epoxies makes agood durable base for the applicationof all topcoats.

Solvent-based self-etching epoxyprimers have a VOC content ofapproximately 3.5 - 4.0 lbs/gal. Withthe addition of the activator andr e d u c e r, the sprayable primer- s u r f a c e rformula has a VOC content of 4.5lbs/gal. Waterborne epoxy primershave a VOC content of less then 2.1lbs/gal for the sprayable product.Acrylic Urethane Primer-Sealers

Urethane primer-sealers providehigh build characteristics with littleor no shrinkage. They also havesuperior holdout properties whichmake them an excellent primer-sealer.

Urethane primer-sealers have aVOC content ranging from 4.3 - 5.0lbs/gal after the addition of theactivator and reducers. Urethanesmust usually be topcoated within 24hours to avoid the need for sandingand recoating.

D. Sealers

Sealers are applied prior to thetopcoat if needed. They should havethe following qualities:

1. Provide adhesion between the topcoat and the surface.

2. Provide a single, neutral-colored base for easy coverage.

3. Seal sanded surfaces to prevent solvent penetration.

4. Fill minor imperfections.

Recommended Practices forPrimer-Sealers

• Use low VOC primer-sealers suchas single component waterborne,or waterborne epoxy primers.


• Always choose primer-sealer color that can be easily covered by the topcoat to be sprayed, or choose a tintable primer-sealer and tint it toan easily covered shade.

A pplication of the topcoat is thenext phase of the surface coating

operation. Topcoats are applieddirectly over the undercoats, whichmay be a prep coat, primer-surfacer,primer-sealer or sealer. Topcoatsi n clude paints and clears that give thesurface the color, gloss and durabilitydemanded by today's consumers.The EPA estimates indicate thattopcoats are responsible for 55 percentof all VOCs released d u r i n g s u r f a c ecoating operations (Figure 18).

Paints are considered to be eithersolid or metallic-type topcoat. Thesolid color paints are made up ofsolvents, binders and opaquepigments that produce the color ofthe finish. Metallic colors are madeup of solvents, binders and opaquepigments like the solid colors, butalso include small light-refractingflakes. These small metallic,polychrome or mica flakes refractsome of the light that enters thefinish, resulting in a surface thatappears richer and deeper in color.The orientation of the refracting

flakes, as well as their locationwithin the finish layer, affect theperceived color and richness of thepainted surface. The positioning ofthese flakes within the finish isdictated by the type of paint, thespeed of the thinner and hardener,the type and settings of the sprayequipment, along with the sprayingtechniques used.

Topcoats are categorized as eithersingle stage or two stage systems.Three stage systems are used bysome automobile manufacturers, butwill not be addressed in this manual.

Many paintcompanies offerthe option ofhigh-solids paintsor clears whichcontain 60percent or moresolids by volume.Solvents such asglycol esters,esters andketones, whichkeep more of thesolids insuspension withless solvent, aregenerally used in

high-solid paints, primers and clears.These systems reduce the amount ofVOCs released by up to 75 percent,while reducing the amount of paintmaterial needed by almost one-halfas compared to conventional systems.Generally, only one to three coats areneeded to achieve adequate coverageusing high solids paints.

High solids paints have a highviscosity in their sprayable form.High viscosity materials are moredifficult to atomize into the finedroplets needed to achieve a quality


9. Topcoats

Topcoats areresponsible for 55%of the VOCs releasedduring surfacecoating operations


Topcoats (55%)

Equipment Cleaning (20%)


A pplication of the topcoat is thenext phase of the surface coating

operation. Topcoats are applieddirectly over the undercoats, whichmay be a prep coat, primer-surfacer,primer-sealer or sealer. Topcoatsi n clude paints and clears that give thesurface the color, gloss and durabilitydemanded by today's consumers.The EPA estimates indicate thattopcoats are responsible for 55 percentof all VOCs released d u r i n g s u r f a c ecoating operations (Figure 18).

Paints are considered to be eithersolid or metallic-type topcoat. Thesolid color paints are made up ofsolvents, binders and opaquepigments that produce the color ofthe finish. Metallic colors are madeup of solvents, binders and opaquepigments like the solid colors, butalso include small light-refractingflakes. These small metallic,polychrome or mica flakes refractsome of the light that enters thefinish, resulting in a surface thatappears richer and deeper in color.The orientation of the refracting

flakes, as well as their locationwithin the finish layer, affect theperceived color and richness of thepainted surface. The positioning ofthese flakes within the finish isdictated by the type of paint, thespeed of the thinner and hardener,the type and settings of the sprayequipment, along with the sprayingtechniques used.

Topcoats are categorized as eithersingle stage or two stage systems.Three stage systems are used bysome automobile manufacturers, butwill not be addressed in this manual.

Many paintcompanies offerthe option ofhigh-solids paintsor clears whichcontain 60percent or moresolids by volume.Solvents such asglycol esters,esters andketones, whichkeep more of thesolids insuspension withless solvent, aregenerally used in

high-solid paints, primers and clears.These systems reduce the amount ofVOCs released by up to 75 percent,while reducing the amount of paintmaterial needed by almost one-halfas compared to conventional systems.Generally, only one to three coats areneeded to achieve adequate coverageusing high solids paints.

High solids paints have a highviscosity in their sprayable form.High viscosity materials are moredifficult to atomize into the finedroplets needed to achieve a quality


9. Topcoats

Topcoats areresponsible for 55%of the VOCs releasedduring surfacecoating operations


Topcoats (55%)

Equipment Cleaning (20%)


dries by solvent evaporation similarto lacquer type coatings. This stagetakes from seven to nine hours,depending on drying conditions. Inthe following six hours to 30 days,the enamel cures due to the oxidationof the binder as it reacts with air.

The drying time, the gloss and thedurability of the finish can all beimproved with the addition of achemical hardener. However, thesehardeners not only reduce the pot-life of the paint, they also releaseisocyanates during spraying andcuring operations.

Alkyd enamels are thinned 15 - 33percent depending on the brand.Only two to three coats usually arerequired to provide adequatecoverage. Alkyd enamels containapproximately 5.0 - 5.5 lbs/gal VOCsin sprayable form, approximately 55- 75 percent VOCs by volume.

Acrylic Enamel

Acrylic enamels are used for bothspot repairs as well as overallp a i n t i n g o p e r a t i o n s. These enamelsoffer more durable finishes andfaster drying times than the alkyde n a m e l s. A c r y l i c enamels dry in fiveto seven hours, with the secondcuring period taking an additionalsix to 72 hours at 72°F.

Drying time, gloss and durabilityof acrylic enamels can all be improvedwith the addition of a chemicalh a r d e n e r. These hardeners increasedthe durability of the surface byalmost 50 percent compared toacrylic enamels without hardeners.

Acrylic enamels, on average,contain 5.0 - 5.5 lbs/gal VOCs intheir sprayable form. With acrylicenamels requiring only two to threecoats to provide adequate coverage,the VOCs are reduced by 45 percentover lacquer type paints.

Enamel products usually do notneed the addition of a flex agent onfairly rigid parts. If used on veryflexible parts, the addition of a flexagent may be required, increasingthe VOC content.

Po lyurethane Enamel SingleStage To p c o a t s

Polyurethane topcoats are a two-part painting system requiring theaddition of a hardener or reactor (thesecond component) to assure propercuring of the finish. Polyurethanetop coats have great spraying charac -teristics along with good metallicflow properties. They produce a highgloss, chemically resistant finish thatwill withstand the effects ofultraviolet radiation for many years.

Polyurethane enamels have a VOCconcentration of 5.0 - 5.5 lbs/gal intheir sprayable form. The high VOCcontent of these coatings is offset bytheir excellent coverage. Normally,only two to three coats are needed toprovide a good quality finish. Po l y -urethane finishes have good flexibilityand can be used over flexible partswithout the addition of flex additives.

Acrylic Urethane Enamel

Acrylic urethanes produce one ofthe most durable automotive finishesavailable today. They have twice thedurability of polyurethanes, with lesscuring time needed to achieve a tackfree finish.

Acrylic urethanes have a relativelyhigh VOC content (ranging from 5.0 -5.5 lbs/gal) in their sprayable form.Generally, only two coats of thesetopcoats are required to produce aquality finish, reducing the amountof material needed for the topcoating process.

9: Topcoats


With acrylic enamelsrequiring only two-three coats to provideadequate coverage,the VOCs are reducedby 45% over lacquers

9: Topcoats


automotive finish. The high solidscoatings, due to their high viscosity,also have poor metallic flakeorientation capabilities compared tolow solids coatings.

Whichever paint system is used, itis important to mix material asspecified by the manufacturer.Today's high-tech finishes, especiallywhen used in the newer HVLP spraye q u i p m e n t , must be mixed accuratelyto produce a high quality finish.Consequently, painters must havethe means to accurately measure thevolumes of paint, reducers, andadditives during mixing. To achievethe proper viscosity of a paint mixturefor specific conditions, a viscosity cup( Figure 5, pg 14) should be used whenmixing all paints and clears. Thiswill help to ensure viscosity of thematerial is adequate to achieve agood quality finish while keepingoverspray and VOCs to a minimum.

To help reduce the amount ofpaint waste and VOCs released, colorcoats should be mixed in-house.Mixing paints in-house allows thefacility to make any tint changesneeded to achieve a color match. Italso gives the technician the freedomto mix only the amount of paintrequired for that specific job. Paintjobbers will generally only mix paintin quantities of one pint or greater.This amount is often more thanneeded, resulting in waste paint.

Spray-out cards with appropriateinformation on the product used andcolor match should be made andcatalogued. This will decrease thetime and money wasted matching acolor, especially considering thenumber of colors and variations ofpaint formulas for each type ofvehicle on the road today.

A. Single Stage Topcoats

Acrylic Lacquer

Lacquer finishes are mostcommonly used for small spot repairoperations due to their fast cure timeand minimal overspray concerns.Lacquer coatings cure solely due tosolvent evaporation, producing ahard, brittle finish.

Because quick evaporatingsolvents are used to thin lacquercoatings, the finish does not have achance to flow adequately prior todrying, resulting in a dull, relativelyrough finish. The fully cured lacquerfinish must be polished to achieve asmooth, high-gloss finish. Usuallyfour to five coats of lacquer areapplied to insure proper paintthickness is maintained afterpolishing.

The hard, brittle coating of thelacquer products is not designed towithstand the flexing of nonrigidsurfaces. For this reason, a flexadditive is used when coating rubberand flexible plastic components withlacquer paints.

To achieve the correct viscosity forconventional spray gun application,lacquer paints are thinned 125 - 150percent. This high solvent concen-tration results in a VOC content of6.0 - 6.5 lbs/gal, 70 - 90 percent byvolume. The EPA estimates that theuse of lacquer paints increases theamount of VOC emissions by 45percent compared to enamel topcoats.

Alkyd Enamel Alkyd enamels are the least

durable of all the automotive paints.Alkyd enamels dry in a two stagecuring process. First, the finish

To help reduce themount of paint wasteand VOCs released,color coats should be

mixed in-house

dries by solvent evaporation similarto lacquer type coatings. This stagetakes from seven to nine hours,depending on drying conditions. Inthe following six hours to 30 days,the enamel cures due to the oxidationof the binder as it reacts with air.

The drying time, the gloss and thedurability of the finish can all beimproved with the addition of achemical hardener. However, thesehardeners not only reduce the pot-life of the paint, they also releaseisocyanates during spraying andcuring operations.

Alkyd enamels are thinned 15 - 33percent depending on the brand.Only two to three coats usually arerequired to provide adequatecoverage. Alkyd enamels containapproximately 5.0 - 5.5 lbs/gal VOCsin sprayable form, approximately 55- 75 percent VOCs by volume.

Acrylic Enamel

Acrylic enamels are used for bothspot repairs as well as overallp a i n t i n g o p e r a t i o n s. These enamelsoffer more durable finishes andfaster drying times than the alkyde n a m e l s. A c r y l i c enamels dry in fiveto seven hours, with the secondcuring period taking an additionalsix to 72 hours at 72°F.

Drying time, gloss and durabilityof acrylic enamels can all be improvedwith the addition of a chemicalh a r d e n e r. These hardeners increasedthe durability of the surface byalmost 50 percent compared toacrylic enamels without hardeners.

Acrylic enamels, on average,contain 5.0 - 5.5 lbs/gal VOCs intheir sprayable form. With acrylicenamels requiring only two to threecoats to provide adequate coverage,the VOCs are reduced by 45 percentover lacquer type paints.

Enamel products usually do notneed the addition of a flex agent onfairly rigid parts. If used on veryflexible parts, the addition of a flexagent may be required, increasingthe VOC content.

Po lyurethane Enamel SingleStage To p c o a t s

Polyurethane topcoats are a two-part painting system requiring theaddition of a hardener or reactor (thesecond component) to assure propercuring of the finish. Polyurethanetop coats have great spraying charac -teristics along with good metallicflow properties. They produce a highgloss, chemically resistant finish thatwill withstand the effects ofultraviolet radiation for many years.

Polyurethane enamels have a VOCconcentration of 5.0 - 5.5 lbs/gal intheir sprayable form. The high VOCcontent of these coatings is offset bytheir excellent coverage. Normally,only two to three coats are needed toprovide a good quality finish. Po l y -urethane finishes have good flexibilityand can be used over flexible partswithout the addition of flex additives.

Acrylic Urethane Enamel

Acrylic urethanes produce one ofthe most durable automotive finishesavailable today. They have twice thedurability of polyurethanes, with lesscuring time needed to achieve a tackfree finish.

Acrylic urethanes have a relativelyhigh VOC content (ranging from 5.0 -5.5 lbs/gal) in their sprayable form.Generally, only two coats of thesetopcoats are required to produce aquality finish, reducing the amountof material needed for the topcoating process.

9: Topcoats


With acrylic enamelsrequiring only two-three coats to provideadequate coverage,the VOCs are reducedby 45% over lacquers

9: Topcoats


automotive finish. The high solidscoatings, due to their high viscosity,also have poor metallic flakeorientation capabilities compared tolow solids coatings.

Whichever paint system is used, itis important to mix material asspecified by the manufacturer.Today's high-tech finishes, especiallywhen used in the newer HVLP spraye q u i p m e n t , must be mixed accuratelyto produce a high quality finish.Consequently, painters must havethe means to accurately measure thevolumes of paint, reducers, andadditives during mixing. To achievethe proper viscosity of a paint mixturefor specific conditions, a viscosity cup( Figure 5, pg 14) should be used whenmixing all paints and clears. Thiswill help to ensure viscosity of thematerial is adequate to achieve agood quality finish while keepingoverspray and VOCs to a minimum.

To help reduce the amount ofpaint waste and VOCs released, colorcoats should be mixed in-house.Mixing paints in-house allows thefacility to make any tint changesneeded to achieve a color match. Italso gives the technician the freedomto mix only the amount of paintrequired for that specific job. Paintjobbers will generally only mix paintin quantities of one pint or greater.This amount is often more thanneeded, resulting in waste paint.

Spray-out cards with appropriateinformation on the product used andcolor match should be made andcatalogued. This will decrease thetime and money wasted matching acolor, especially considering thenumber of colors and variations ofpaint formulas for each type ofvehicle on the road today.

A. Single Stage Topcoats

Acrylic Lacquer

Lacquer finishes are mostcommonly used for small spot repairoperations due to their fast cure timeand minimal overspray concerns.Lacquer coatings cure solely due tosolvent evaporation, producing ahard, brittle finish.

Because quick evaporatingsolvents are used to thin lacquercoatings, the finish does not have achance to flow adequately prior todrying, resulting in a dull, relativelyrough finish. The fully cured lacquerfinish must be polished to achieve asmooth, high-gloss finish. Usuallyfour to five coats of lacquer areapplied to insure proper paintthickness is maintained afterpolishing.

The hard, brittle coating of thelacquer products is not designed towithstand the flexing of nonrigidsurfaces. For this reason, a flexadditive is used when coating rubberand flexible plastic components withlacquer paints.

To achieve the correct viscosity forconventional spray gun application,lacquer paints are thinned 125 - 150percent. This high solvent concen-tration results in a VOC content of6.0 - 6.5 lbs/gal, 70 - 90 percent byvolume. The EPA estimates that theuse of lacquer paints increases theamount of VOC emissions by 45percent compared to enamel topcoats.

Alkyd Enamel Alkyd enamels are the least

durable of all the automotive paints.Alkyd enamels dry in a two stagecuring process. First, the finish

To help reduce themount of paint wasteand VOCs released,color coats should be

mixed in-house

achieve low solids and low VOCcontent is through the usewaterborne technology.

Early versions of waterbornebasecoats were very sensitive toatmospheric conditions in the booth.Waterborne paints generally containless than 10 percent solvents(excluding water and exemptsolvents) by weight. To achieveproper crosslinking of the coating,both the water and the othersolvents must evaporate at the sametime and rate. This will not occur ifthe humidity is above the acceptablerange of that coating (generally 65 -80 percent). High humidity and/orlow temperatures also increase thecuring time of the finish, and increasethe possibility of runs and sags.

In order to achieve a good qualityfinish, humidity and temperature ofthe booth must be closely regulated.In an industrial setting, paintingconditions can be closely monitoredto provide an ideal paintingenvironment. In the repair industry,such control can not be adequatelyachieved without expensive controldevices. Modern paint booths caneffectively control applicationtemperature as well as curingconditions, but booth humidity

remains relatively unchecked.

To help combat the difficultiesassociated with the early waterbornesystems, new waterbornetechnologies were developed.Currently, there are two types ofwaterborne basecoats beingproduced, acrylic latex and urethanepolymer. Both use melamineformaldehyde polymers as the basicfilm former. The addition of thesepolymers and glycol ethers has beeninstrumental in controlling the flowof waterborne basecoat finishesduring topcoating operations. Sincethe initial stage of curing is nolonger dependent on the rate ofwater evaporation, the need forexpensive humidity control devicesare no longer necessary. Adequateair movement within the spray boothis necessary to assist in the curing ofthe waterborne coating. This hasmade waterborne basecoattechnology accessible to the autorepair industry. These systems arenow being utilized in the regulatedareas of the west coast with somesuccess. However, waterbornecoatings are still susceptible to coldweather and must be protectedfrom freezing during transportationand storage.

9: Topcoats


Advantages of Waterborne Basecoat Systems✇ Low VOC content of the sprayable product (2.5 - 3.5).

✇ Good metallic flake orientation properties.

✇ Good atomization properties.

✇ No catalyst is needed for the latex basecoat, only the clear will require the addition of a catalyst.

✇ No flash time is required between color coats.

Currently, the onlyway to achieve thelow solids and VOCcontent is throughthe use ofwaterbornetechnology

9: Topcoats


B. Two Stage Basecoat/ Clearcoat Topcoats

It has been estimated that nearlyhalf of the automobiles on the roadtoday have a basecoat / clearcoatfinish. The first stage of the finish,the basecoat, contains the pigmentsthat give the finish the desired color.In the case of metallic finishes, thebasecoat also contains the "metallic"flakes.

When basecoat / clearcoat systemsfirst came out, the basecoats wereprimarily lacquer based. Today, paintcompanies are producing acrylicenamel, polyester, and urethanebasecoats; all of which have bettermetallic control then their lacquercounterparts. The basecoat isdesigned to be easy spraying andquick drying with excellent metalcontrol. The quick-drying effect isdesigned to keep the base free of dirtand other contaminants. It alsolocks the metallic flakes in positionto achieve a mottle-free finish.

The sole purpose of the basecoat isto achieve the desired color tint andmetallic appearance. Only two coatsof the base are normally needed toachieve adequate surface coverage.Basecoats do not contain theadditives needed to withstandchemical and ultraviolet deterio-ration or the chemicals needed toachieve a high gloss surface.

To protect the basecoat, a durableclear finish is applied. This clearcoating can often be applied over thebase after only 15 to 30 minutes ofcure time. Commonly the VOCcontent of the basecoats range from6.0 - 7.0 lbs/gal.

Clearcoats are typically acrylicurethane or polyurethane coatings,

although acrylic enamel and lacquerclears are also available. Theseclears are designed to flow uponapplication resulting in a smooth,glass-like finish in as few as twocoats.

VOC content of the clears rangesfrom 5.0 - 5.5 lbs/gal in theirs p r ayable form. Many of the majorpaint companies are producing lowVOC clears (3.5 lbs/gal or less) foruse with basecoat / cl e a r c o a ts y s t e m s. These low VO C, h i g h - s o l i dclears create a high-gloss finishwith half the materials of a lowsolids cl e a r.

Waterborne Basecoat Systems

Waterborne basecoats arecurrently being used by a smallnumber of automobile manufacturingplants in North America. But withthe implementation of stricter VOCregulations, these coatings areexpected to gain popularity withinthe industry. VOC content of thesewaterborne basecoats is relativelylow, ranging from 2.5 - 3.5 lbs/gal intheir sprayable form.

The waterborne technology useswater as the main solvent, givingthese basecoats low VOC emissionswhile retaining low solids content.The low solids level means greatermetallic control, resulting in auniform finish free of mottling.Some experts note that to achievethe optimal metallic flakeorientation, the volume of solids in acoating must be less than 20 percentby weight. Yet to achieve compliancewithin the regulated areas of the U. S. ,the solids volume in solvent basedbasecoats must be in excess of 45percent. Currently, the only way to

VOC content ofwaterborne base

coats is relativelylow, ranging from2.5 - 3.5 lbs/gal

achieve low solids and low VOCcontent is through the usewaterborne technology.

Early versions of waterbornebasecoats were very sensitive toatmospheric conditions in the booth.Waterborne paints generally containless than 10 percent solvents(excluding water and exemptsolvents) by weight. To achieveproper crosslinking of the coating,both the water and the othersolvents must evaporate at the sametime and rate. This will not occur ifthe humidity is above the acceptablerange of that coating (generally 65 -80 percent). High humidity and/orlow temperatures also increase thecuring time of the finish, and increasethe possibility of runs and sags.

In order to achieve a good qualityfinish, humidity and temperature ofthe booth must be closely regulated.In an industrial setting, paintingconditions can be closely monitoredto provide an ideal paintingenvironment. In the repair industry,such control can not be adequatelyachieved without expensive controldevices. Modern paint booths caneffectively control applicationtemperature as well as curingconditions, but booth humidity

remains relatively unchecked.

To help combat the difficultiesassociated with the early waterbornesystems, new waterbornetechnologies were developed.Currently, there are two types ofwaterborne basecoats beingproduced, acrylic latex and urethanepolymer. Both use melamineformaldehyde polymers as the basicfilm former. The addition of thesepolymers and glycol ethers has beeninstrumental in controlling the flowof waterborne basecoat finishesduring topcoating operations. Sincethe initial stage of curing is nolonger dependent on the rate ofwater evaporation, the need forexpensive humidity control devicesare no longer necessary. Adequateair movement within the spray boothis necessary to assist in the curing ofthe waterborne coating. This hasmade waterborne basecoattechnology accessible to the autorepair industry. These systems arenow being utilized in the regulatedareas of the west coast with somesuccess. However, waterbornecoatings are still susceptible to coldweather and must be protectedfrom freezing during transportationand storage.

9: Topcoats


Advantages of Waterborne Basecoat Systems✇ Low VOC content of the sprayable product (2.5 - 3.5).

✇ Good metallic flake orientation properties.

✇ Good atomization properties.

✇ No catalyst is needed for the latex basecoat, only the clear will require the addition of a catalyst.

✇ No flash time is required between color coats.

Currently, the onlyway to achieve thelow solids and VOCcontent is throughthe use ofwaterbornetechnology

9: Topcoats


B. Two Stage Basecoat/ Clearcoat Topcoats

It has been estimated that nearlyhalf of the automobiles on the roadtoday have a basecoat / clearcoatfinish. The first stage of the finish,the basecoat, contains the pigmentsthat give the finish the desired color.In the case of metallic finishes, thebasecoat also contains the "metallic"flakes.

When basecoat / clearcoat systemsfirst came out, the basecoats wereprimarily lacquer based. Today, paintcompanies are producing acrylicenamel, polyester, and urethanebasecoats; all of which have bettermetallic control then their lacquercounterparts. The basecoat isdesigned to be easy spraying andquick drying with excellent metalcontrol. The quick-drying effect isdesigned to keep the base free of dirtand other contaminants. It alsolocks the metallic flakes in positionto achieve a mottle-free finish.

The sole purpose of the basecoat isto achieve the desired color tint andmetallic appearance. Only two coatsof the base are normally needed toachieve adequate surface coverage.Basecoats do not contain theadditives needed to withstandchemical and ultraviolet deterio-ration or the chemicals needed toachieve a high gloss surface.

To protect the basecoat, a durableclear finish is applied. This clearcoating can often be applied over thebase after only 15 to 30 minutes ofcure time. Commonly the VOCcontent of the basecoats range from6.0 - 7.0 lbs/gal.

Clearcoats are typically acrylicurethane or polyurethane coatings,

although acrylic enamel and lacquerclears are also available. Theseclears are designed to flow uponapplication resulting in a smooth,glass-like finish in as few as twocoats.

VOC content of the clears rangesfrom 5.0 - 5.5 lbs/gal in theirs p r ayable form. Many of the majorpaint companies are producing lowVOC clears (3.5 lbs/gal or less) foruse with basecoat / cl e a r c o a ts y s t e m s. These low VO C, h i g h - s o l i dclears create a high-gloss finishwith half the materials of a lowsolids cl e a r.

Waterborne Basecoat Systems

Waterborne basecoats arecurrently being used by a smallnumber of automobile manufacturingplants in North America. But withthe implementation of stricter VOCregulations, these coatings areexpected to gain popularity withinthe industry. VOC content of thesewaterborne basecoats is relativelylow, ranging from 2.5 - 3.5 lbs/gal intheir sprayable form.

The waterborne technology useswater as the main solvent, givingthese basecoats low VOC emissionswhile retaining low solids content.The low solids level means greatermetallic control, resulting in auniform finish free of mottling.Some experts note that to achievethe optimal metallic flakeorientation, the volume of solids in acoating must be less than 20 percentby weight. Yet to achieve compliancewithin the regulated areas of the U. S. ,the solids volume in solvent basedbasecoats must be in excess of 45percent. Currently, the only way to

VOC content ofwaterborne base

coats is relativelylow, ranging from2.5 - 3.5 lbs/gal

9: Topcoats


D. Recommended Practices for Topcoats•Mix color coats in-house, making certain the formula for the proper shade

of the specific color code is used. This will help avoid the need for blending of the finish to achieve a satisfactory color match.


•Avoid the use of lacquer-based topcoats.

•Choose low VOC topcoats that require fewer than three coats to achieve adequate coverage (polyurethane or urethane).

•Only apply the number of coats needed to achieve an adequate finish.•Use high solids, low VOC clears to topcoat color coats.•The addition of paint additives should be kept to a minimum.•When available, use waterborne basecoats.

9: Topcoats


C. Paint AdditivesAlong with the chemical hardeners

and flex additives previouslymentioned, there are many otherpaint additives available. Theseinclude flatting compounds,accelerators, retarders, color blendersand fisheye eliminators. Theaddition of any one of these

additives not only affects the spraya-bility of the product and the qualityof the finish, it also increases theVOC content of that system. To keepVOC emissions low and materialcosts down, the use of additivesshould be kept to a minimum.

Advantages, con’t✇ Waterborne basecoats have superb hiding properties and generally require only two coats for complete coverage.

✇ Equipment can be cleaned with water instead of solvents.

✇ At least one waterborne paint manufacturer offers a coagulating agent that will separate the solids from the cleanup water, allowing the water to be reused while reducing the volume of waste generated.

Disadvantages of Waterborne Basecoat Systems✇ Current mixing systems need to be modified or replaced to accommodate

waterborne basecoats.

✇ All waterborne products must be transported and stored in such a manner as to protect them from freezing.

✇ All spray equipment used to apply waterborne coatings will need to be ofa material such as stainless steel to protect against corrosion.

✇ Booth temperature and adequate air movement is essential for achievinga finish free of runs and sags.

✇ To hasten curing, infrared drying systems or forced air curing systems may be needed.

✇ Waterborne products are more susceptible to substrate contamination than are solvent-borne products.

✇ The waste water/paint mixture resulting from equipment cleanup operations may require more expensive disposal fees than solvent/paint wastes.

The use of anyadditives canincrease VOC

content

9: Topcoats


D. Recommended Practices for Topcoats•Mix color coats in-house, making certain the formula for the proper shade

of the specific color code is used. This will help avoid the need for blending of the finish to achieve a satisfactory color match.




•Only apply the number of coats needed to achieve an adequate finish.•Use high solids, low VOC clears to topcoat color coats.•The addition of paint additives should be kept to a minimum.•When available, use waterborne basecoats.

9: Topcoats


C. Paint AdditivesAlong with the chemical hardeners

and flex additives previouslymentioned, there are many otherpaint additives available. Theseinclude flatting compounds,accelerators, retarders, color blendersand fisheye eliminators. Theaddition of any one of these

additives not only affects the spraya-bility of the product and the qualityof the finish, it also increases theVOC content of that system. To keepVOC emissions low and materialcosts down, the use of additivesshould be kept to a minimum.

Advantages, con’t✇ Waterborne basecoats have superb hiding properties and generally require only two coats for complete coverage.

✇ Equipment can be cleaned with water instead of solvents.

✇ At least one waterborne paint manufacturer offers a coagulating agent that will separate the solids from the cleanup water, allowing the water to be reused while reducing the volume of waste generated.

Disadvantages of Waterborne Basecoat Systems✇ Current mixing systems need to be modified or replaced to accommodate

waterborne basecoats.

✇ All waterborne products must be transported and stored in such a manner as to protect them from freezing.

✇ All spray equipment used to apply waterborne coatings will need to be ofa material such as stainless steel to protect against corrosion.

✇ Booth temperature and adequate air movement is essential for achievinga finish free of runs and sags.

✇ To hasten curing, infrared drying systems or forced air curing systems may be needed.

✇ Waterborne products are more susceptible to substrate contamination than are solvent-borne products.

✇ The waste water/paint mixture resulting from equipment cleanup operations may require more expensive disposal fees than solvent/paint wastes.

The use of anyadditives canincrease VOC

content


10. Recommended Approach to PracticalAir Emission Reduction

Spray Equipment• Determine how much you are willing to spend for spray equipment.


• Prior to purchasing any paint gun, consult your paint representative to determine what type of gun will work best for the products you will be using.

• Contact your paint representative and/or paint gun representative to determine the fluid tip/air cap combination and gun settings that should be used with the material being sprayed.

• Choose spray equipment that has the highest transfer efficiency while providing the required atomization properties within your price range.

Spray Application Techniques• Use the recommended air pressure and tip sizes for the specific product and



• Feather the trigger at the beginning and end of each pass.

• Use a 50 percent overlap for each pass. This technique may need to be altered slightly when applying high-metallic, high-solids basecoats, and for some three stage systems.


• With larger panels, use a comfortable stroke, with a 4 - 5 " overlap of the strokes.



• Use color hiding power labels to determine the thickness of the applied paint film. These markers will also indicate when adequate coverage has been achieved.


10. Recommended Approach to PracticalAir Emission Reduction

Spray Equipment• Determine how much you are willing to spend for spray equipment.


• Prior to purchasing any paint gun, consult your paint representative to determine what type of gun will work best for the products you will be using.

• Contact your paint representative and/or paint gun representative to determine the fluid tip/air cap combination and gun settings that should be used with the material being sprayed.

• Choose spray equipment that has the highest transfer efficiency while providing the required atomization properties within your price range.

Spray Application Techniques• Use the recommended air pressure and tip sizes for the specific product and



• Feather the trigger at the beginning and end of each pass.

• Use a 50 percent overlap for each pass. This technique may need to be altered slightly when applying high-metallic, high-solids basecoats, and for some three stage systems.


• With larger panels, use a comfortable stroke, with a 4 - 5 " overlap of the strokes.



• Use color hiding power labels to determine the thickness of the applied paint film. These markers will also indicate when adequate coverage has been achieved.

10: Recommended Approach to Practical Air Emission Reduction


Primer-surfacers con’t

• If a colored sealer is not used, make sure the primer-surfacer is a color that can easily be covered with the desired topcoat.

Primer Sealers• Use low VOC primer-sealers such as single component waterborne or

waterborne epoxy primers.


•Always choose a color of primer-sealer that can be easily covered by the topcoat to be sprayed or choose a tintable primer-sealer and tint it to an easily covered shade.

Sealers•Chose the proper sealer for each specific job.

•If filling capabilities are required, use a primer-sealer in place of a sealer.

• Always choose a primer-sealer of a color that can be easily covered with the coating to be sprayed, or choose a tintable primer-sealer.

Topcoats•Mix color coats in-house, making certain the formula for the proper shade of

the specific color code is used. This will help avoid the need for the blending of the finish to achieve a satisfactory color match.

• Keep good records of paint match information, including spray-out cards and detailed notes.



• Apply only the number of coats needed to achieve an adequate finish.

•Use high solids, low VOC clears to topcoat color coats.

• Keep addition of paint additives to a minimum.

• When available, use waterborne basecoats.



Equipment Cleaning•Use an air powered mechanical gun cleaning system.


•If cleaning guns manually, spray into an enclosed backdrop to retain atomized solvents.

• If necessary, use a broom straw, cleaning broach or a soft wood toothpick to clear passageways. Never use metal objects.

Surface Prep• Always wash dirt and grime from the vehicle using water or a soap and water

mixture.

• Use waterborne cleaners when possible.

•If, due to heavy contamination, waterborne cleaners prove unsatisfactory, use solvent-based cleaners for the initial cleaning. For secondary cleaning operations, use the waterborne products.

• If waterborne cleaners prove unsatisfactory due to substrate make-up, use solvent-based cleaners sparingly.

• Keep solvent laden dirty rags in a closed container.

• Keep solvent containers closed when not in use.

•If possible, avoid operations that would necessitate multiple prepaint cleaning operations.

Prep Coats• Use versatile products such as epoxy primers or self-etching primers. The use

of these products may alleviate the need for additional surface coating operations such as primer-surfacing or primer-sealing.

• If a self-etching primer or epoxy primer is not desirable, use a wash-primer or metal conditioner, conversion coating system.


Primer-Surfacers• Use a properly operating primer gun with the correct fluid tip/air cap

combination for your particular type of primer-surfacer.

• Use low VOC, waterborne primer-surfacer products.

•If the curing time of waterborne products proves unsatisfactory, consider the use of versatile urethane primers.




Primer-surfacers con’t

• If a colored sealer is not used, make sure the primer-surfacer is a color that can easily be covered with the desired topcoat.

Primer Sealers• Use low VOC primer-sealers such as single component waterborne or

waterborne epoxy primers.


•Always choose a color of primer-sealer that can be easily covered by the topcoat to be sprayed or choose a tintable primer-sealer and tint it to an easily covered shade.

Sealers•Chose the proper sealer for each specific job.

•If filling capabilities are required, use a primer-sealer in place of a sealer.

• Always choose a primer-sealer of a color that can be easily covered with the coating to be sprayed, or choose a tintable primer-sealer.

Topcoats•Mix color coats in-house, making certain the formula for the proper shade of

the specific color code is used. This will help avoid the need for the blending of the finish to achieve a satisfactory color match.

• Keep good records of paint match information, including spray-out cards and detailed notes.



• Apply only the number of coats needed to achieve an adequate finish.

•Use high solids, low VOC clears to topcoat color coats.

• Keep addition of paint additives to a minimum.

• When available, use waterborne basecoats.



Equipment Cleaning•Use an air powered mechanical gun cleaning system.


•If cleaning guns manually, spray into an enclosed backdrop to retain atomized solvents.

• If necessary, use a broom straw, cleaning broach or a soft wood toothpick to clear passageways. Never use metal objects.

Surface Prep• Always wash dirt and grime from the vehicle using water or a soap and water

mixture.

• Use waterborne cleaners when possible.

•If, due to heavy contamination, waterborne cleaners prove unsatisfactory, use solvent-based cleaners for the initial cleaning. For secondary cleaning operations, use the waterborne products.

• If waterborne cleaners prove unsatisfactory due to substrate make-up, use solvent-based cleaners sparingly.

• Keep solvent laden dirty rags in a closed container.

• Keep solvent containers closed when not in use.

•If possible, avoid operations that would necessitate multiple prepaint cleaning operations.

Prep Coats• Use versatile products such as epoxy primers or self-etching primers. The use

of these products may alleviate the need for additional surface coating operations such as primer-surfacing or primer-sealing.

• If a self-etching primer or epoxy primer is not desirable, use a wash-primer or metal conditioner, conversion coating system.


Primer-Surfacers• Use a properly operating primer gun with the correct fluid tip/air cap

combination for your particular type of primer-surfacer.

• Use low VOC, waterborne primer-surfacer products.

•If the curing time of waterborne products proves unsatisfactory, consider the use of versatile urethane primers.


T he automotive refinishingindustry has undergone many

significant changes in the last tenyears, with even greater changesanticipated within the next decade.The Clean Air Act Amendmentsrequire implementation of newstringent emission control andpermitting requirements within thenext ten years. Although it is not yetclear what specific regulations are instore for the automotive refinishingindustry, it is clear that some form ofemission regulations will be imposed.Impending regulations are alreadycausing many changes within thepaint manufacturing and applicationequipment industries.

Paint manufacturers are focusingtheir efforts on the development ofpaints and primers that will meetthe rigid standards of the future.VOC contents of topcoats willprobably be limited to 5.0 lbs/gal orl e s s, while undercoats may be limitedto as low as 3.5 lbs/gal. Paint manu-facturers will continue emphasizingdevelopment of waterborne and high-solids paints and primers.

Waterborne paints will probablybe limited to basecoats which willrequire the application of a urethaneclearcoat. The use of glycol ethers,esters, ester alcohols and water assolvents for paint products willcontinue to increase. Other highsolvency products such as propyleneglycol and methyl butyl ethers willalso gain popularity with paintmanufacturers.

High viscosity, high solids paints

and primers may require modifi-cation of current paint practiceswithin the refinishing industry.Paint-heaters may be essential inevery paint shop to lower theviscosity of the high-solids solvent-based paints and primers prior tospraying. Heaters are not effectivewith waterborne paints due to theirlack of effect on these products'viscosity.

The spray equipment used by thetypical paint shop will be of theHVLP variety. High transfer-efficient spray equipment willcontinue to improve, providing thetechnician with better atomizationand metallic control.

Recently, a new paint system hasbeen developed using super-criticalcarbon dioxide (CO2) in place ofsolvents to lower the viscosity of thecoating. These systems reduce VOCemissions from 25 percent to asmuch as 80 percent, depending onthe coating used. Currently, the useof these systems is limited toindustrial painting; the finish qualityneeded for the application ofautomotive finishes has yet to bea ch i e v e d . As the technology improvesand investment costs lower, CO2

systems may be used on a limitedscale for auto refinishing operations.

Automobile refinishers will beunable to rely solely on low VOCproducts and high transfer efficientspray equipment to reduce VOCemissions. Employers will also needto train their painters and preptechnicians in the proper use of allexisting and new equipment andproducts entering the market place.Spray paint techniques must also be


11. What to Expect inthe Future

The spray equipment used by thetypical paint shopwill be of the HVLPvariety.

T he automotive refinishingindustry has undergone many

significant changes in the last tenyears, with even greater changesanticipated within the next decade.The Clean Air Act Amendmentsrequire implementation of newstringent emission control andpermitting requirements within thenext ten years. Although it is not yetclear what specific regulations are instore for the automotive refinishingindustry, it is clear that some form ofemission regulations will be imposed.Impending regulations are alreadycausing many changes within thepaint manufacturing and applicationequipment industries.

Paint manufacturers are focusingtheir efforts on the development ofpaints and primers that will meetthe rigid standards of the future.VOC contents of topcoats willprobably be limited to 5.0 lbs/gal orl e s s, while undercoats may be limitedto as low as 3.5 lbs/gal. Paint manu-facturers will continue emphasizingdevelopment of waterborne and high-solids paints and primers.

Waterborne paints will probablybe limited to basecoats which willrequire the application of a urethaneclearcoat. The use of glycol ethers,esters, ester alcohols and water assolvents for paint products willcontinue to increase. Other highsolvency products such as propyleneglycol and methyl butyl ethers willalso gain popularity with paintmanufacturers.

High viscosity, high solids paints

and primers may require modifi-cation of current paint practiceswithin the refinishing industry.Paint-heaters may be essential inevery paint shop to lower theviscosity of the high-solids solvent-based paints and primers prior tospraying. Heaters are not effectivewith waterborne paints due to theirlack of effect on these products'viscosity.

The spray equipment used by thetypical paint shop will be of theHVLP variety. High transfer-efficient spray equipment willcontinue to improve, providing thetechnician with better atomizationand metallic control.

Recently, a new paint system hasbeen developed using super-criticalcarbon dioxide (CO2) in place ofsolvents to lower the viscosity of thecoating. These systems reduce VOCemissions from 25 percent to asmuch as 80 percent, depending onthe coating used. Currently, the useof these systems is limited toindustrial painting; the finish qualityneeded for the application ofautomotive finishes has yet to bea ch i e v e d . As the technology improvesand investment costs lower, CO2

systems may be used on a limitedscale for auto refinishing operations.

Automobile refinishers will beunable to rely solely on low VOCproducts and high transfer efficientspray equipment to reduce VOCemissions. Employers will also needto train their painters and preptechnicians in the proper use of allexisting and new equipment andproducts entering the market place.Spray paint techniques must also be


11. What to Expect inthe Future

The spray equipment used by thetypical paint shopwill be of the HVLPvariety.

11: What to Expect in the Future


improved to reduce overspray toreduce material waste and VOCemissions. This will require paintersto have additional training in properspraying techniques using the newhigh transfer spray equipment.

It will take the efforts of all paintrelated industries to provideadequate reduction of VOCs and

HAPs. Changes in coating products,spray equipment and applicationtechniques will all be met with someresistance. But with continuedcooperation and education, harmfulVOC and HAP emissions fromrefinishing operations will be drama-tically reduced, creating a cleanerand healthier environment for all.

The Iowa Waste Reduction Center has developed andpatented the Laser Touch TM

targeting system to helpimprove transfer efficiency, and reduce overspray andmaterial consumption. The Laser Touch TM

is designedto provide spray technicians with a “real-time” means of

assessing their spray technique and improving their spray performance. Ituses a split laser beam image to provide the spray gun operator with avisual indication of gun-to-part distance, gun angle and targeting.

The Laser Touch TMhas proved to be the most well received and productive

training tool used in the Spray Technique Analysis and Research program.STAR trainees using the Laser Touch TM

have shown dramaticimprovements in maintaining a consistentspray distance, proper gun angle, uniformcoating thickness and improved transferefficiency. The following comments arerepresentative of statements made byLaser Touch TM

users:

• “I cannot believe my spray distance varied that much, this device helps me immediately in keeping me consistent.”

• “Quite frankly, it’s perhaps one of the biggest money saving devices that we have ever seen come about it this industry.”

• “This is great for both experienced painters as well as the beginners.”

For more information on the LaserTouch TM

call the IWRC at 319-273-8905.

LaserTouch

TM

11: What to Expect in the Future


improved to reduce overspray toreduce material waste and VOCemissions. This will require paintersto have additional training in properspraying techniques using the newhigh transfer spray equipment.

It will take the efforts of all paintrelated industries to provideadequate reduction of VOCs and

HAPs. Changes in coating products,spray equipment and applicationtechniques will all be met with someresistance. But with continuedcooperation and education, harmfulVOC and HAP emissions fromrefinishing operations will be drama-tically reduced, creating a cleanerand healthier environment for all.

The Iowa Waste Reduction Center has developed andpatented the Laser Touch TM

targeting system to helpimprove transfer efficiency, and reduce overspray andmaterial consumption. The Laser Touch TM

is designedto provide spray technicians with a “real-time” means of

assessing their spray technique and improving their spray performance. Ituses a split laser beam image to provide the spray gun operator with avisual indication of gun-to-part distance, gun angle and targeting.

The Laser Touch TMhas proved to be the most well received and productive

training tool used in the Spray Technique Analysis and Research program.STAR trainees using the Laser Touch TM

have shown dramaticimprovements in maintaining a consistentspray distance, proper gun angle, uniformcoating thickness and improved transferefficiency. The following comments arerepresentative of statements made byLaser Touch TM

users:

• “I cannot believe my spray distance varied that much, this device helps me immediately in keeping me consistent.”

• “Quite frankly, it’s perhaps one of the biggest money saving devices that we have ever seen come about it this industry.”

• “This is great for both experienced painters as well as the beginners.”

For more information on the LaserTouch TM

call the IWRC at 319-273-8905.

LaserTouch

TM

Documents

Auto Body Surface Coating Guide