INDEX

S. No. Particulars

1 Introduction

2 History

3 Main Features

4 Equipment and Materials

5 Methods of Screen Making

6 Types of Screen

7 Advantages & Disadvantages of Screen

printing

8 Screen printing Defects and their remedies

9 Modern Development

10

GOVT. WOMEN’S POLYTECHNIC COLLEGE

UDAIPUR (RAJ.)

PROJECT REPORT

ON

RAJASTHANI AMBROIDARY

2009-10

Submitted By

PUSHPA SUKHWAL

Textile Design (Third year)

Principal Project Incharge

Mr Syed Irshad Ali Mrs. Kavita Mathur

GOVT. WOMEN’S POLYTECHNIC COLLEGE

Udaipur (Raj.)

(Board of Technical Education Rajasthan, Jodhpur)

Department of Textile Design

CERTIFICATE

This is to certify that Miss Pushpa Sukhwal D/o Sh. Bhanwer Lal

Sukhwal, Govt. Women’s Polytechnic College, Udaipur (Raj.), Third

year [Textile Designing] has completed her project work integrately

under my guidance and supervision from 17 May 2010 to 12 June 2010.

During her stay with me, I have found her obedient and hard

working. We wish her all success in her life.

Mr. Syed Irshad Ali Mrs. Kavita Mathur

Principal Project Incharge

ACKNOWLEDGEMENT

I take the proud privilege to acknowledge my sincere thanks and

gratitude’s to Mr. Syed Irshad Ali, Principal and Mrs. Kavita Mathur,

Lecture for their guidance of encouragement.

Our gratitude’s towards Mrs. Kavita Mathur for making our

project tenure, a pleasant experience of the different experience of the

different practical works, which can be of job oriented, If enhance our

practical work professionally.

I would also like express our feeling to the lab staff of our college

for helping and supporting as morally of giving there cheerful company

during the project work.

I am also thankful to all those people who directly or indirectly

helped me to complete my project.

Sincerely

PUSHPA SUKHWAL

WHAT IS PROJECT

Hypothetically project means the physical existence of librating ideas

of the human mind. The meaning of project can be viewed by

explaining into individual letters.

P - Stands for planning which is done for designing the project.

R - Stands for reliable source from where we are getting the

materials.

O - Stands for overall experience of the project prepared.

J - Stands for joint effort to design the project correctly.

E - Stands for economy mean for the project is much

economic.

C - Stands for construction, which is the important part of the

project.

T - Stands for technique used to construct they device. In this

way we can say that the project is the mirror of the life of a

designers.

INTRODUCTION

Screen printing is simply an improved method of stencil printing in

which no “ties” are required, thus giving designers much wide : scope and

freedom in planning his design than the earlier methods. The main difference

between the two methods is that in screen printing the ordinary stencil plate

is replaced by a tightly stretched screen of thin silk gauze on which the

pattern is painted in such a way that the unpainted parts correspond to the

perforations in a stencil plate and perform exactly the same function i.e. they

allow the colour paste to pass through them freely on to the cloth placed

beneath. In stencil printing, colour is usually applied by brush but in screen

printing, it is applied by means of a rubber or wooden squeegee which is

almost as wide as the screen. The structure of the screen permits patterns of

almost any size to be handled with ease and certainty. Due to the absence of

“ties”, it is possible to introduce circles and rings and continuous lines and

produce patterns of almost any style and any dimension without fear of the

stencil telling to pieces.

HISTORY

Although the screen process itself is of modern introduction, men long

ago cut stencils and applied colour one way or another though the stencil

openings and onto desired surfaces – much as use today apply addresses on

creates and boxes in our shipping rooms.

Stencil printing was done by the ancients, some authors crediting the

Egyptians with the discovery. The Chinese, Japanese and fiji Islanders are

variously credited by other writers but such claims are mere suppositions and

no definite evidence ever has been put forth to verify them.

Stencil printing was used in England and France in the 17 th and 18th

centuries for the production of wallpaper and methods akin to the modern

silk screen principle were secretly employed in Europe prior to the invention

of lithography (1978). The clean has been made that the process was first

used in Germany about 1870, and others contend that it originated in

England before 1900.

The first definite historical date in the evolution of the silk screen

apparently is 1907, for it was in that year that a British patent was grauted to

Samuel simon for a tieless stencil

MAIN FEATURES OF SCREEN PRINTING

(1) Screen printing is an advantage over block printing as less pressure in

to be exerted.

(2) Screen Printing is simple process and any one can install a small

machine and can start the printing work at lower cost.

(3) Delicate and intricate design can be produce by screen printing.

(4) Multi coloured designs can be produce early as compared to block.

(5) Advantage of roller or copper plate printing are also obtained in screen

printing.

(6) Ease of work in using more than 2 colours or 3-4 colours can be

obtained as against the difficulties of taking more than 6 colours in

roller printing.

(7) No Extra ordinary skill in required to under take screen printing. It’s

just a matter of experience & practice.

(8) Screen printing is economical as the production rate in high.

(9) The print obtained are intense, more bright and passes natural bloom,

that what is obtained in block or copper plate printing.

(10) Sharp outlines and fine vertical lines can be produced which is not

possible in block printing.

(11) It is possible to print any type of fabric or garment like knitted, rayon

synthetic etc. by screen printing processes.

EQUIPMENTS AND MATERIALS FOR SCREEN PRINTING

1- Screen Frame

2- Screen Fabric

3- Squeeze

4- Screen Printing inks

5- Printing Table

6- Exposing Table

7- Printing Paste

(1) Screen Frames

Smooth surfaced picture frames that have not warped and have strong,

secure corners joints can be used. Any protruding nails or projections must

be removed.

Otherwise frame can be made from ordinary 50 mm (2”) by 25 mm

(1”) planed, well seasoned, straight-grained safe-wood corners which must

be square can be but jointed, water proof glued pinned with 50mm (2”) oval

nails. The completed frame should be flat and be smooth with band-paper

before it is painted all over with exterior-quality varnish. The corners can be

strengthened by metal brackets.

A convenient screen for printing small articles and all over stripes of

softwood, each 375 mm (15”) long by 50 mm (2”).

Although larger screen can be made to print the whole with of the

cloth at once they usually require two people to handle.

Types of Frame

Wooden Frame Metal Frame Stripe Frame Base Frame

(a) Wooden Frame :

The bolting cloth is stretched tightly over and fixed to a strong

wooden frame which are usually 15 to 20 cm wide than the cloth to be

printed and also 15 – 20 cm larger than the vertical repeat of the

pattern.

It is necessary to maintain the atmosphere which is free from moisture

and dust.

(b) Meal Frame :

Metal frames are preferred to wooden frames as they last longer.

These are used for hand as well as in automatic screen-printing.

(c) Stripe Frame :

This frame consists of tucked wooden stripes which in warpped all

around the screen design. It has small pores on holes on it.

(d) Box Frame :

This is better than stripes frame. It has a metal or wooden frame work

on which corners are attached inside the frame which are positioned

on the inside of frame at ¼” (6 mm) generally oak wood or metal is

used for frame at ¼” (6 mm) generally oak wood or metal is used for

frame.

(2) Screen Fabrics

Cloth is the most important material of screen printing. The transfer of

design with ink on the printable surface is through this fabrics. It should be

care fully selected generally – Nylon, Organdie, Silk, Metal cloth and bolting

cloth is used for screen fabric. Every fabric has its even quality.

(a) Silk :

This is a fine weaved cloth and has very tiny perforations in between

weaving. It could be seen by a magnifying glass. The fiber the

weaving the fiber the perforations. The no. of perforations are asserted

by mesh. In silk there are 2 – 25 mesh.

(b) Nylon :

This is synthetic fabric is widely used now a days gauze this cloth is

strong. The no. of mesh is 16 – 465 / inch.

(c) Organdie :

This fabric is used in place of silk. This is not as strong as silk or

nylon and has quich effect of water and air. The fabric of screen gets

loosen up automatically. This is of a standard mesh i.e. 109 mesh/inch

which is equal to 11 No. silk.

(d) Metal Cloth :

This is a fine metal cloth which is usually made of copper and

stainless steel. These fabric are strong and fine. The screen made of

these fabric can be used for years. These are also known as wire cloth.

(e) Bolting Cloth :

This is originally a silk fine uniform mesh. This fabric is weaved with

gum and no. of thread / inch is light. It’s standard width is 40”. This

fabric can be of fine mesh cotton muslin. At one time for making

vinyon or filament yarn Vinyon Acitate’s co-polymer and Vinyl

chloride were used. But when the production of these yarn was

stopped synthetic yearn was used. Bolting cloth is also known as

Bendral. Many a times bolting cloth is used in floor mills. Bolting

cloth is good for inferior quality application / work. This is Rs. 100/m.

(3) Squeeze

(a) Hand Squeeze

(b) Automatic squeeze system

(c) Hand Squeeze

The squeeze is used to push the dye through screen. It was initially

made of wood usually having wooden handles, than sharp blades were used

with wooden squeeze but this tends to cut the wooden frame, so a more

durable way was to invented.

The squeeze was then made of a hand rubber or plastic strip sand

wiched between two lengths of wood which also known a handle. It should

slightly smaller then the inside width of the frame and wider then the

window or the design in side it.

The small household window-cleaner is excellent for small screen and

has the additional advantages of learning one had free to hold the screen

while printing, file down any sharp corner to avoid damaging the screen

covering.

A very cheap hardboard squeeze can be cut to the sharp, but be certain

that all edges are smoothened and corner rounded and that the edge of the

blade is straight.

Automatic Squeeze System

Rotary Screen Squeeze System Flat Bed Squeeze System

1. Aljaba squeeze 1. Busser Flat Bed Squeeze

2. Stork Rotary Squeeze 2. Zimmer Flat bed Squeeze

3. Buser Rotary Squeeze

4. Zimmer Rotary Squeeze

1. Aljaba Squeeze

Each unit has central adjusting device to hold the screen in the screen

in the squeeze unit. This ensure quick and accurate fine setting and

quick screen changing. If a narrow-width screen is used it can be

placed in a special unit with telescope tubes each squeeze unit has its

own motor and a two speed gearing provides for two squeeze speed of

640 mm and 922 mm/sec. The centrifugal break of this squeeze unit

ensure soft starting accurate stopping and the no. of strokes and the

pressure can be individually adjusted for each unit. The speed of the

whole machine has to be geared to the speed of the undertaking the

most strokes 1, 2, 8, 4 squeeze strokes can be arranged, the desirable

no. is a mater for experience and as per the design requirements, the

quality of cloth and the viscosity of print paste.

2. Strok Rotary System :

A squeeze proper with a squeeze profile and a colour supply pipe. The

special fitting of the holder on to the supply pipe prevents bending of

the squeeze. Even in the care of printing width of 120” or more.

Flexible steel pipes are best suited. The squeeze is vertically adjusted

single of the blade can be easily adjusted or doctor which is moved

upward can also be attached.

3. Buser Rotary Squeeze System :

It has a special circular squeeze system which remain at its home

portion in the starting then, when the printing paste is filled, the air

pad swell and the squeeze is lowered down in printing problem. After

the application of printing paste the squeeze again comes in its

original home positions and printing paste released again and colour is

returned from the screen to the colour basin.

4. Zimmer Roatary Squeeze System :

This machine employs the magnet roll system of pressing the colour

through the screen. The magnet rolls squeeze and works down the

cloth, at sight angles to the selvedge. There are a no. of advantages

claimed for this invention. One is that no uneven wear takes place on

the rods as can accure with a blade type squeeze. A high rate of

production can be maintained, gauge fabrics can be satisfactorily

printed by a single stroke of the rod.

(b) Flat Bed Squeeze System

(i) Buser Flat bed Squeeze system is same as Alkaba rotary

squeeze system.

ii) Johannes Zimmer Flat bed Squeeze System.

A special system known as magnet roll system in used to push colour

through the mesh. The other squeeze used in other machines operate from

selvedge to selvedge whereas this squeeze work down the cloth, at right

angles to the selvedge.

(4) Screen Printing Inks :

There are many types of inks used in printing on the basis of their :

(a) According to Transparency

(b) On the basis of Luster

(c) On the basis of Base

(a) According to Transparency

(i) Transparent :

No ink is fully transparent. One colour ink printing is done at

one time. Then second colour ink is used and if over lapped a

third colour is automatically produced.

(ii) Opaque :

These are the inks which are used on the printing cloth often

which the fabric surface is not visible secondly, light colour /

shade design can be produced on dark background.

(b) On the Basis of Luster :

(i) Matt Ink :

It is mainly used on wood for eg. Cricket bats, carom board etc.

Because of matt effect it takes less time in drying.

(ii) Semi Glose Ink :

This ink is very lustrous is generally used for printing banner. It

dries in 2 – 3 hours.

(iii) Glose Ink :

This is used in fancy advertisement, calendars, visiting cards

etc. takes 10 – 12 hours to dry.

(iv) Fluorescent Ink :

The materials printed from this ink have lustrous print dazzle in

sunlight. Generally advertisement banners etc. are printed,

which are attractive in appearance. It takes short period of time

in drying and is costly.

(v) Venie Shine Ink :

This ink is lustrous is generally used for printing leathers rubber

paper, hard board and banners and some metal. It takes 15

minutes to dry.

(c) On the Basis of Base :

(i) Oil Base Ink :

This ink is used to print paper, wood, cardboard, leather,

regxine etc. This type of ink is known as silk screen. This is

mainly used in screen-printing. This ink is also used to print to

tins or containers.

(ii) Ceramic Ink :

This ink is mainly used on glass, rust plate etc. The printing on

radio dial is also done with this ink. Crockery is also print with

this ink.

(iii) Label Ink :

This ink is known as PVC ink is general. The printing on purse,

diary couers etc. is done with this ink.

(iv) Textile Ink :

This ink is used on textile material like – sarees, bedspreads,

dress material etc. Generally this ink is used in big industries

instead of ordinary screen-printing. This ink is not available in

small packages and is very costly.

(v) Nitro Cellulose Ink :

This ink is costlier than oil based ink. Some low salts are

present in the ink and some crystal crystal are also present and

its also dries faster.

(vi) Catalile Ink :

This ink is used on glass, plastic, sand board, scientific

equipment, Jalar, glass paper etc. for decoration. It is also used

on motor car dress for transparency and clarity. It has good

solidity, flexibility, resiliency, durable and fixation quality.

(vii) Printed Circuit Ink :

This ink is used resistant. This ink is used for printing copper

foil sheet in this film.

(viii) E-Hec Ink :

This is based on methyl hydroxyl – Ethyl cellulose and is most

widely used now a days. This is opaque and is soluble in white

spirit. This is cheaper.

(ix) Lacquer Based Ink :

This ink is used to print plastic sheets, PVC sheet and other

material with the help of screen. This ink can be easily applied

on the surface where other inks are not available.

(5) Printing Table (For Cloths)

(a) Hand Screen Printing Table :

In the initial days, when the screen printing started the table used

where heavy wooden once which were covered with thick felt and a gray

cloth, to prevent the wood from being worn out it was wrapped with cloth or

any other material. Then metal or concrete table was used which are still

used. Table is covered with felling blankets and gray fabrics. Table should

be of 30 inch – 60 inch in length and breadth should be 10” – 12” broader

than cloth to be printed for ease of work.

Now a days the tables are 60 yards in length 30” in height and 48” –

62” in breath. The thickness of felting is 6 mm. The elasticity and flexibility

is must for every printing table. If the printed cloth is to be fixed on the

surface of the table than waterproof or water less adhesive should be used.

And also waterproof covering are used for screen printing top. They are –

1. Rubber Material :

Nitro Cellulose is a cotted material. The adhesives used in it are :

Rubber solution /sheet

Destrin/ allopage or neuopage

Poly Vinyl Alcohol

Based on nitro cellulose

The recipe of this adhesive

Paraffin Wax = 530 gm.

Petroleum Jelly = 280 gm.

Resin = 190 gm.

(6) Poly Vinyal Alcohol :

This is used for coating the screen frame. It is a photosensitive

chemical.

Some of the gum that can be used are :

(a) Natural Gum

(b) Arabic Gum

This two are mixed and applied on table.

II. Automatic Screen Printing Table

There is a little difference in today’s hand and Automatic screen

printing table. The difference lies in the glueing or fixing of fabric an

the table.

III. Buser Automatic Screen Printing Table

IV. Stork Automatic Screen Printing Table

V. Zimmer Automatic Screen Printing Table

VI. Flat Bed Screen Printing Table

VII. Rotary Screen Printing Table

Printing Table for Paper

It is made of wood either of sunmica or glass. A wooden sheet is

attached to the one end of the table with the help of knobs or screws.

This sheet gives support at the time of printing the paper.

(7) The Printing Paste

The essential ingredients of a printing paste are selected from the

following :

(a) Dyestuffs, Pigments or dyestuff preaursors. [Dyestuff Formers].

(b) Wetting Agents

(c) Solvents, Solution, Aids, Dispersing agents and humertants

(d) Thickness

(e) Defoaming agents

(f) Oxidizing and reducing agents

(g) Catalysts and Oxygen Carriers

(h) Acid and Alkalies

(i) Carries and Swelling agents

(j) Miscellaneous agents

(a) Dyestuffs :

Coloured objects acquire their true colours because they absorb a

definite portion of white light and unaffecting the rest. Some dyestuffs

are water insoluble.

(b) Wetting agents :

When a wooden stick or a glass rod is dipped in water it will be seen

that some water sticks to it on removing the same from water. But if

the stick is coated with oil or molten was and cooled then dipped is

water no water sticks to it. This happens because oil and water ‘hate’

each other and the oil coated or wax coated surfaces are called

hydrophobic (water hating) surfaces. Surfaces that can be wetted with

water easily are called hydrophilic (water hating) surfaces. Surfaces

that can be wetted with water easily are called hydrophilic (water

Leveling) surface and main feature of this factor is to make a dye

smooth. T.R.O., Monopol, Brilliant Oil agent are used. Vat dye,

Naphtl dye to make soluble by wetting agent.

(c) Solvents :

Solvents or dispersing agents are used to prevent aggregation of the

dyestuff molecules in the high concentrated paste of the dye.

Commonly used solvents Acetin, Tetralene, Decarbon etc.

(d) Thickners :

Thickners used in textile printing are high molecular weight

compounds giving viscous pastes in water. Their main function is to

hold or adhere the dye particles in the desired place on the fabric until

the transfer of the dye into the fabric and its fixations are complete.

Printing Thickeners

Natural Modified Natural Synthetic

Cereals Starch (Maize, Wheat etc.) Starch derivatives British gums Acrylic Polyacrylic acid

(destrin carboxymethyl) methyl Polyacrylamide

starch

Plant Exudates Gum Tragacanth Cellulose derivatives carboxy methyl Vinyl Polyvinyl alcohol

Roots & Seeds Guar Gum Locust Gum derivatives meyprogum Indalca

Gum

Sea weeds Sodium alginate Gum

(e) Defoaming Agents :

Defoamers are used in the paste. Perminal KB of ICI is a defoamer.

Emulsified pine oil and silicones are used as defoamers. When added

to printing pastes containing direct, acid, vat or disperse dyes it exerts

an anti forming effect.

(f) Oxidizing and Reducing Agents :

Mild oxidizing are used to prevent reduction of dyes during steaming

as otherwise the dye may get partially destroyed due to reducing

frames.

Reducing agent is used mainly in discharge printing. Sodium

hydrosulphate is a well known reducing agent used in the printing of

Vat dyes by the pre-reduction method.

(g) Catalysts :

These are used to accelerate the development of colours by oxidizing

agent and reduce the risk of their attaching the fiber for example

copper sulfide.

(h) Acid and Alkalies :

Wesk acids like citric acid, tartaric acid etc. are used to make the paste

acidic where required. Citric or tartaric acid is used in the disperse dye

paste since acetic acid in rotatile and escapes during high temperature

staming.

(i) Carriers :

These are mainly used for fixing disperse dye on polyster or polyster

wood blends at temperature below 1050 C same of their trade names

are – Tumes col O.P., Tumescol D is used as a carrier.

(j) Miscellaneous :

The dye at the printed portion is reduced and solubilised and this form

of the dye react with the complexing agent.

Preparation of the Printing Paste

The main objective in printing to produce coloured designs in one or

more cololurs with sharp boundaries on textile material, without any of the

dyes spreading beyond the boundaries of the design. In order to achieve this

a concentrated dye solution has to be prepared with minimum of water and

thickened with a suitable thickening agent. Such a starch, gum etc.

Dissolution of a type in a very small amount of water in plies that special

solution aids or solvents should be used in the printing paste during its

preparation. Same of their ingredients used in the preparation of a printing

paste. All these are not used in a single printing paste but depending on the

class of the dye being printed and the style of printing selected, different

ingredient are used.

Printing Paste of Acid Dye

Chemical :

According to wt. of gum

Natural gum

Tartaric acid

Sulphuric acid

Acid dye

Time – 2 hours.

Procedure :

Weight the sieved gum now take acid dye according to wt. of gum. It

is dissolved in water and boiled for 5 min. Now add gumboil it for another

20 min. Than add dilute tartaric acid and sulfuric acid to it. Boil it for

another 15 minute and than add use a to it. After boiling this paste for 2

hours, let it to cold now, when cooled it is ready to be used for printing.

Printing Paste of Rapid Dye

Chemical :

According to wt. of gum rapid dye

T. R. O.

Caustic soda

Water

Time – 1 hours

Weight the sieved gum now take rapid dye according to wt. of gum

and take T. R. O., mix both (dye and T. R. O.) and make it in paste four.

Now take some take warm water and add to the paste. Boil it for few min.

Then add caustic Soda to it. Than add gum now boil to make a thick paste

for 15 – 20 min. After the paste thickness switch-ff banner and let the paste

to be cold now it is ready to be used for printing.

Pigment Printing Paste

Chemical :

According to wt. of binder

Acrafix

Urea

Acromion / Pigment dye

Water

To times the paste it required

Procedure :

Mix all the above ingredients and stiffer well. The printing paste it is

now ready. Now pour this paste on screen and spread it evenly with the help

of squeeze from end to end. Then lift the screen and let the fabric printed to

be dried.

BASIC EQUIPMENT

Large plastic buckets, bowls, pons, rod and jars in which to mix dyes

and to as dye baths for cold dyes. Hot dyes will require saucepans or dye

baths to with stand head.

Large and small spoons, metal tape, clear adhesive tape, convector

heater or air-dryer, rubber gloves, overall and apron, clean rag, sponge, dry

clean newspapers, g bolt or g clam, rope, cotton etc.

Material of equipment’s used for :

(a) Constructing frame

(b) Table saw

(c) Miler bore

(d) Corner Clamps

(e) Small drilled

(f) Carpenters Square

(g) Nail set

(h) Jack hammer

(i) Screw driller etc.

METHODS OF SCREEN MAKING

There are four methods of employed for making screen, out of which

photographic method is most important and widely used. It was discovered

by about.

(i) Direct Painting Method

The silk screen is painted by hand with a paint, blocking out the

portions which are not required to be printed.

(ii) Profilm Method

Profilm is a cellulose acetate with shellac and a backing paper is

placed over the design to be produced and the required motif are

cutout with a sharp knife so as to form a stencil. This stencil is placed

on the silk screen and hot ironed where by the acetate melts and gets

fixed on to the screen. Which after peeling off the backing paper is

ready for use.

(iii) Resist Method

A suitable resist is obtained on the screen in the required design, to

dry and then the whole surface of this screen coated with a suitable

lacquer. After drying the screen is washed with warm water, removing

the resist.

(iv) The Photographic Method

This requires considerable experience and still and it very widely

used. The silk bolting cloth stretched on the screen frame is coated

with a sensitizing solution and gelatin dichromate or polyvinyl alcohol

dichromate and is dried in the dark.

The screen is first sensitized or made photo – sensitive by applying to

it either.

(a) Gelatine – Dichromate solution

(b) Polyvinyal Alcohol dichromate solution as indicated below

(a) Gelatine – dichromate solution :

Preparation :

200 gm. Gelatine in

500 ml. boiling water

And then dissolving 70 gm. ammonium dichromate in 150 ml. boiling

water and 80 ml. liquor ammonia and mixing the two solution in a dark

room. This mixture is applied to the bolting cloth at 500C and allowed to dry

in a dark room. The table with a glows top fixed with tube lights inside is

used for exposure of the screen. The positive is placed on the glass top of the

table fixed by an adhesive tape. All is than exposed to light for about 15 min.

The operation is carried out in an orange safe light.

Treating it with a cold solution containing hardens the screen.

25 gm. ammonium dichromate

50 gm. chrome alum and

50 cm. formal dehyde (40%)

Pre liter for 10 min, washed in cold water and allowed to dry. It is

further rain forced by applying a lacquer such as Bed a fin 200 ltr. Or 210 ltr.

of ICI.

(b) P.V.A.

Preparation :

600 gm. P.V.A. (15% solution)

120 ml. ammonium dichromate

Solution (33%) and

240 ml. water and making up to 1 ltr.. It is strained and applied to the

screen at 400C by a scraper in daylight and allowed to dry. It is

exposed to light and then hardened by treating it for 1 ltr. in a solution

containing.

50 ml. acetaldehyde

50 ml. isolutyraldehyde and

Retouching and Reinforcing the screen – The pin holes are blocked by

P.V.A. or lacquer. The screen is now prepared for the printing.

TYPES OF SCREEN PRINTING

Hand Screen Printing

When screen printing was first developed it was done entirely by

hand. A frame of wood was stretched tightly with five silk or organdie, on to

which the pattern was transferred. A fabric known as ‘bolting silk’ which

had been created for flour-milling sieves was used for a number of year. The

warp thread in this special silk were fixed in position between two twisted

weft threads, so ensuring a completely stable base on which to engrave a

pattern. This transference of the pattern was, and still can be done is a great

variety of way from the extremely simple one of painting out the background

with varnish to the most advanced of photomechanical techniques.

Adapting the design

Preparing a design for screening apply equally to preparing one for

any other repeat process but this is a suitable place to insert the details to

correcting repeats because hand screen printing is a method widely practices.

When preparing the tracing each colour in the design needs a separate sheet

of kodatrce or other transparent tracing.

Stretching the screen

A wooden frame is taken and a bolting of required mesh is fixed on

the frame with the help of iron nails and rope. It is tightly fixed so that it

could be exposed and printed properly.

Coating the screen

After the screen frame is prepared the chemicals photo chemical

P.V.A. and potassium dichromate mixed and applied and coated on the

screen with the help of blade or scale evenly on both the side of the screen.

After the coating of this layer, the screen is left to dry in the same dark room.

Because the screen gets exposed in contact with any kind of light.

Exposing the screen

After the screen dries it is exposed on the exposing table kept in the

same dark room. The Kodak already prepared the design made on the

negative film by crokel pen and water proof ink or otherwise prepared the

designed butter paper by the computer is kept and fixed on the glass of the

exposing table and screen is kept over it. Pressure of mud or stones is

applied on the screen for uniform and clear exposing. The lights of the

exposing table are now switched on and a times is set for 7-8 min. After the

time is over the timer alarm automatically switches on the lights are now

switched off the screen it put under water.

Retouching and Reinforcing

The screen is now inspected for pinholes and blocked design which is

cleared accordingly. The pinholes are blocked by P.V.A. or lacquer. The

screen is now prepared for printing.

Printing Process

The colour paste is first poured at the bottom end of the shallow

through of the screen and drawn over with two or three strokes of the

squeeze with uniform pressure whereby the colour in transferred to cloth

underneath. The screen is then lifted from this position (i) To position (3)

repeating the operation than to position (5) So on (missing one position each

time) to avoid making off of colour until the whole table length is covered.

The cloth is then dried by heating the tables of by blowing hot air and

printing is carried out in position (2), (4), (6) etc. until the whole length is

printed with colour.

Each screen is washed with a jets of water immediately after use

because if it is left to dry with the colour paste on it, it because difficult to

clean it later and can even block the mesh of the screen rendering it useless.

The printed cloth after drying is removed and given appropriates after

treatments.

Advantages of Hand Screen Printing

1. The method enable new pattern to be produced quickly and without

a large initial expenses. Since the screens can be produced cheaply.

2. It is use full for printing knitted fabrics of rayon, which cannot be

manipulated satisfactorily on the roller printing machineries.

3. It is economical in production and manually less exacting than

block printing.

4. Both designs can be printed by this method.

5. As many as 16 colours can be printed in one pattern by this

method, in roller printing even through it is possible to be that it is

difficult is practice to use more than 6 rollers.

6. Prints obtained by it are more intense, more bright and posses

natural bloom. By using fine mesh screen sharp outline and vertical

lines can be produced.

7. The method is simple to operate and does not require elaborate and

expensive equipments.

Disadvantages of Hand Screen Printing

1. A large no. of tables is required for higher production, requiring

huge space.

2. Delicate shading and gradation of colour are difficult to obtain.

3. Joint marks at the repeats are after perceptible get choked

rendering the screen.

Advantage of Screen Printing

1. The method is simple to operate and does not require elaborate and

expensive equipment.

2. The method enables new patterns to be produced quickly and

without a large initial expense, since the screens can be produced

cheaply.

3. The method is useful for printing knitted rayon fabrics which

cannot be manipulated satisfactorily on the rotor printing machine.

4. The method is economical in production and manually less

exacting than block printing.

5. Block design can be printed by this method which cannot be

printed by block or roller printing further, it is possible to produce

larger repeats than those in roller printing.

6. As many as 16 colours can be printed in one pattern by this method

in roller printing even though it is possible to do this, it is difficult

in practice to use more than 6 rollers.

7. Prints obtained by this method are more intense, more bright and

possess natural bloom as compared with those obtained by roller

printing method, further by using fine-mesh screens, sharp line

effects including vertical lines can be produced by this method

which are difficult to produce with roller printing.

Disadvantages of screen Printing

1. For high production, a large number of tables have to be used

requiring huge space with incidental overheads in roller printing

the space required is very much less.

2. Delicate shading and gradation of colour are difficult to obtain by

this method and the joint marks at eh repeats are often perceptible.

3. Fine-mesh screens used for sharp line effects often get choked

rendering the screen redundant.

SCREEN PRINTING DEFECTS AN THEIR REMEDIES

The defects that occur in screen printing are not as many as those

which occur in roller printing because being a hand printing process, the

defects which arise in a machine due to say, doctor blade or roller engraving

are absent in screen printing. Other defects and the remedies thereof are as

under :

(i) Uneven Prints : These occur if the printing table is not level or if the

edge of the rubber squeeze is uneven. The remedy lies in using a

perfectly level table and sharpening the edge of the squeeze.

Badly bleached cloth also give rise to uneven prints due to uneven

absorption of colour, the remedy is to use a well bleached cloth.

(ii) Lighter Prints : These arise if the openings of the screen get clogged

particularly by pigment colours which dry up too soon: the remedy

lies in washing the screen immediately after use because it is difficult

to clean the openings once the synthetic resin (binder) is set.

Lighter prints are also caused if the colour paste is too thick the thick

paste produces a weak impression because it is too; solid to be

absorbed freely. The remedy is to thin down the paste. Foam produced

in the paste also causes lighter prints; the remedy lies in adding anti-

foaming agents like pine oil, turpentine or cyclohexanol to the paste.

(iii) Specks of dark colour : These appear as minute specks on the cloth

due to faulty colour mixing; the remedy is to mix the ingredients

properly.

Small specks on the unprinted portions of the cloth appear due to Pin

holes on the screen formed due to constant working of the screen or

due to negligence of the screen maker. The remedy is to check the pin

holes and cover them with lacquer.

(iv) Light and dark prints : These appear on the selvedges if the pressure

on the squeeze is uneven or the steaming in the Star Ager is not

uniform; uneven appear due to batchwise steaming on batch rollers.

The remedy is to apply pressure on the squeeze evenly, ensure proper

steaming and avoid too much loading on the roller.

Once the cloth is badly printed, it is difficult to rectify the defect;

therefore, great care has to be taken to prevent the faults and to rectify the

same immediately so that the number of rejects to the minimum.

MODERN DEVELOPMENTS

Rotary screen printing has proved to be the ideal modern printing

method. It has seemingly infinite capacity for adaptability printing textiles,

wallpapers, carpet, back and front coating and foam printing; transformer

printing, warp printing. The most important factor in the industry in

flexibility, and it would seem that forecast made for the method are being

widely fulfilled not only can rotary screen machines accomplish all the

above but the screens are textural effect formerly attributed to engraved

roller as well as much, it not all which is possible by hand screen. Therefore

the method can be used for all classes of work from small quantities of

sophisticated fabrics to mans production and with the advent of laser

engraving of rotary screen in 1986/87 speed, exactness and an immense

variety of style are possible, soon all repeat size will be possible too.