Designation: D 2395 – 07a

Standard Test Methods forSpecific Gravity of Wood and Wood-Based Materials1

This standard is issued under the fixed designation D 2395; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.

This standard has been approved for use by agencies of the Department of Defense.

1. Scope

1.1 These test methods cover the determination of thespecific gravity of wood and wood-based materials to generallydesired degrees of accuracy and for specimens of differentsizes, shapes, and moisture content conditions. The methodtitle is indicative of the procedures used or the specific area ofuse.

SectionMethod A—Volume by Measurement 7Method B—Volume by Water Immersion 8Method C—Flotation Tube 9Method D—Forstner Bit 10Method E—Increment Core 11Method F—Chips 12

1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.

2. Referenced Documents

2.1 ASTM Standards: 2

D 9 Terminology Relating to Wood and Wood-Based Prod-ucts

D 2555 Practice for Establishing Clear Wood Strength Val-ues

D 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base Materials

D 4444 Test Methods for Use and Calibration of Hand-HeldMoisture Meters

E 1547 Terminology Relating to Industrial and SpecialtyChemicals

3. Terminology

3.1

3.1.1 green volume, n—the solid wood volume before anyshrinkage occurs due to drying to moisture content below thefiber saturation point (about 30 %).

3.1.2 moisture content, n—in this standard, the amount ofwater contained in wood, expressed as a percentage of the massof oven-dry wood.

3.1.2.1 Discussion—In general, the amount of water inwood can be expressed on two different bases: as a percentageof the mass of oven-dry wood, or a percentage of the total massof wood and water. To avoid misunderstandings, it must beclear which basis is being used. In the forest industry and thewood products industry, the moisture content is usually ex-pressed as a percentage of the mass of oven-dry wood.

3.1.3 specific gravity, n—in this standard, the ratio of theoven-dry mass of a specimen to the mass of a volume of waterequal to the volume of the specimen at a specified moisturecontent.

3.1.3.1 Discussion—As both the mass and volume of woodvary with the amount of moisture contained in the wood,specific gravity as applied to wood is an indefinite quantityunless the conditions under which it is determined are clearlyspecified. The specific gravity of wood is based on theoven-dry mass, but the volume may be that in the oven-dry,partially dry, or green condition. For further discussion, seeAppendix X2.

3.1.3.2 specific gravity at X % moisture content, n—specificgravity based on oven-dry mass of wood and its volume at aspecified moisture content (X %) between the oven-dry condi-tion and the fiber saturation point (volume at 12 % moisturecontent is frequently used).

3.1.3.3 specific gravity, basic, n—specific gravity based onoven-dry mass of wood and its green volume.

3.1.3.4 specific gravity, oven-dry, or on oven-dry basis,n—specific gravity based on oven-dry mass of wood and itsoven-dry volume.

4. Summary of Test Methods

4.1 The accuracy of the specific gravity value obtained on arepresentative specimen will depend upon the accuracy of themeasurements made. If the specimens are carefully preparedand regular in shape, the volume determined by Method A canbe quite exact. The volume of irregularly shaped specimenscan best be determined by immersion in water and if due care

1 These test methods are under the jurisdiction of ASTM Committee D07 onWood and are the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods and Properties.

Current edition approved July 1, 2007. Published July 2007. Originally approvedin 1965. Last previous edition approved in 2007 as D 2395 – 07.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.

1

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is taken to prevent absorption of water, Method B will giveresults of great precision. Method C is an approximate methodbut a procedure that can be very useful, particularly as part ofa production procedure. Methods D and E are especiallyadapted to gravity measurements of living trees or of in-placeelements and the accuracy of the result is dependent upon thecare used in obtaining the specimen. Method F is a specificprocedure for wood chips.

5. Significance and Use

5.1 The specific gravity of wood gives an excellent measureof the amount of wood substance present in a sample. Thus, itmay serve as a valuable indicator of the amount of wood pulpthat could be produced, the workability of the material, or thestrength characteristics of a specimen or a species. It should berecognized that specific gravity varies between trees, within atree, and between species. Since the specific gravity of woodsubstance is practically constant for all species (approximately1.53), it is apparent that individual specific gravity values areindicative of the amount of wood substance present. It affordsa rapid and valuable method for selection of wood for specificuses.

5.2 It may be desirable to know the specific gravity of aliving tree, a structural member already in place, a log crosssection, a segment of a research element, or the earlywood orlatewood layer. The specimen thus may be large or small,regular or irregular, and at a variety of moisture contents. Thesetest methods give procedures that include all of these variablesand provides for calculation of specific gravity values todegrees of accuracy generally needed.

6. Test Specimens

6.1 The specific gravity specimens shall be fully represen-tative of the material from which they are taken. The specimensize shall be such that accurate measurements of mass andvolume are easy to attain. Where other standards specify thelocation and size of specific gravity specimens, these require-ments shall be carefully followed. The specimens shall becarefully cut from the larger element to ensure clean-cutsurfaces. All loose fibers shall be carefully removed before thespecimen is weighed and measured. The specimen shall be freefrom knots, and if pitch or other infiltrates are present, this shallbe noted in the report or they shall be extracted before specificgravity values are obtained.

6.2 Measurements—The dimensions of test specimens shallbe measured to a precision of 60.3 % or less, and the massshall be determined to a precision of 60.2 % or less. Wheredrying of specimens is required, this shall be done in an ovenmaintained at 103 6 2°C. (For most panel materials and woodspecimens 1 in. (25 mm) in length parallel to grain, drying for48 h in an oven having good air circulation and exchange willbe sufficient to reach constant mass.)

7. METHOD A—VOLUME BY MEASUREMENT

7.1 Applicability:7.1.1 Shape of Specimen—The specimen must be regular in

shape with right-angle corners for determination of volume bylineal measurement. The procedure is adaptable to any size of

specimen or to specimens of any moisture content. If thesurfaces of the specimen are smooth and sufficient measure-ments are taken, the volume can be obtained with considerableaccuracy. Special care must be taken in measurement of verysmall or thin specimens. Volume of irregular or rough-surfacedspecimens should be obtained by Method B.

7.2 Procedures7.2.1 Measurement—Measure the length (L), width (w), and

thickness (t) of the specimen in accordance with 6.2 in asufficient number of places to ensure an accurate indication ofvolume. In small specimens, uniform in size, one or twomeasurements of each dimension will suffice; in larger speci-mens the number of measurements will depend on the unifor-mity of the specimen, but at least three measurements of eachdimension will be required.

7.2.2 Mass—Determine the initial mass (I) of the specimenat the time of test in accordance with 6.2.

7.2.3 Moisture Content—Determine the moisture content(M) of the specimen to permit description of the basis on whichthe specific gravity is computed. Test Methods D 4442 andD 4444 indicate procedures that should be used.

7.2.4 Small Specimens—The entire specimen may be usedfor determination of moisture content.

7.2.5 Intermediate Specimens—When the specimen is of asize that is unsuitable for moisture content determinations (thetime to oven-dry to constant mass would be excessive), asegment may be cut from the specimen for a moisture contentspecimen. Select this segment so that its moisture content isrepresentative of that of the larger specimen. Where possible insolid wood elements, the moisture content specimen shall be offull cross-sectional dimensions and 1 in. (25 mm) in length(parallel to grain). In sheet materials the specimen shall beequal in thickness to the thickness of the material and 3 by 6 in.(76 by 122 mm) in size.

7.2.6 Structural Elements—In full-sized members, deter-mine the moisture content from a segment cut from themember. It shall be of full cross-sectional dimensions and 1 in.(25 mm) in length (parallel to grain), and shall be selected froma representative area of the member. To avoid the effects of enddrying, cut the specimen at least 18 in. (457 mm) in from theend of the member.

7.2.7 Special Situations—Where the specimen or elementcannot be cut to secure a moisture content segment, anapproximate moisture content may be obtained through the useof a moisture meter which is used in accordance with themanufacturer’s recommendations. Since the moisture contentvalue is approximate, it should be recognized that the specificgravity value obtained will also be approximate.

7.2.8 Specimen Preparation—When the moisture contentspecimen is a portion of the element, remove all loose particlesfrom the specimen and determine the initial mass (I) inaccordance with 6.2.

7.3 Drying—Oven-dry the moisture content specimen toconstant mass in accordance with 6.2, and determine theoven-dry mass (F).

8. METHOD B—VOLUME BY WATER IMMERSION

8.1 Applicability

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8.1.1 Type of Specimen—This procedure is particularlyadaptable to specimens of irregular shape or having a roughsurface. Limitations on specimen size are based primarily onsize of immersion tanks available. In small size specimens, lessthan 1 cm3 in volume, air bubbles adhering to the specimensurface can result in considerable error in volume measurementand thus to the computed specific gravity value. Freshly cutgreen wood will not absorb appreciable quantities of waterduring the brief immersion period. As soon as any drying of thewood has taken place however, the surface must be sealedbefore immersion in water or else the volumetric displacementof the wood specimen will be in error in an amount equal to thevolume of water absorbed by the wood.

8.2 Procedures8.2.1 Mass—Determine the initial mass (I) of the specimen

at time of test in accordance with 6.2.8.2.2 Volume—Determine the volume of the specimen by

one of the following modes. Volume may be determined in theas received condition if the specimen is green; or in the asreceived condition if the specimen is partially dry or afteroven-drying if the pores are adequately sealed (see 8.2.2.5).Determine the volume of the specimen by measuring thevolume of water displaced or by determining the mass of thewater displaced. The mass in grams is numerically equal to thevolume in cubic centimetres.

8.2.2.1 Mode I—Place the specimen in a tank of knownvolume and add sufficient water to fill the tank. Then removethe specimen and determine the volume of water remaining.The tank volume less the volume of water remaining is equalto the volume of the specimen. The relationship betweenspecimen volume and tank volume shall be such that theprecision of specimen volume measurement is high.

8.2.2.2 Mode II—Place a container holding enough water tocompletely submerge the specimen on one pan of a balance asshown in Fig. 1. Then balance the combined mass of thecontainer and water with mass added to the other pan. Hold thespecimen so that it is completely submerged without touchingthe sides of the container by means of a sharp, pointed, slenderrod and balance the scales again. The mass added to restorebalance is equal to the mass of water displaced by thespecimen. Alternatively, an automatic balance may be used and

will greatly facilitate the speed of such measurements. If verysmall specimens are used, the accuracy of resulting data islikely to be low.

8.2.2.3 Mode III—Place a container holding enough waterto completely submerge the specimen below one pan of abalance as shown in Fig. 2. The container shall be sufficientlylarge so that immersion of the specimen causes no materialchange in water level. Suspend a wire basket of sufficient massto hold the specimen submerged from this same pan andimmerse it in the water. Balance the mass of the basket whenfreely immersed with mass added to the other scale pan. Weighthe specimen in air. Place the specimen in the basket and holdit completely submerged without touching the container whilebalancing the scales again. The mass added to restore balance,if the specimen is lighter than water, plus the mass of thespecimen in air equals the volume of water displaced. If thespecimen is heavier than water, subtract the mass added torestore balance from the mass of the specimen in air todetermine the volume of water displaced.

8.2.2.4 Mode IV—Immerse the specimen, of an elongatedshape, in a graduated tube having a cross section only slightlylarger than that of the specimen as shown in Fig. 3. Read thewater level in the tube, preferably to an even graduation mark,before immersing the specimen. Immerse the specimen, hold itsubmerged with a slender pointed rod if necessary, anddetermine the water level again. The difference in water levelis equal to the volume of the specimen.

8.2.2.5 Surface Treatment of Specimen— Green specimensmay be immersed in water for volume determinations withoutmaterial absorption of water that will affect volume determi-nations. Dip air-dry or oven-dry specimens in hot paraffin waxbefore making volume determinations. After the wax dip,weigh the specimen again and use this mass in conjunctionwith the immersed mass for determining volume in Mode IIand Mode III (8.2.2.2 and 8.2.2.3). Alternatively, softwoodspecimens or hardwood specimens with small pores may bedipped in a solution of paraffin wax in carbon tetrachloride: 1oz of paraffin wax in 260 in.3 of carbon tetrachloride (1 g ofparaffin wax in 150 cm3 of carbon tetrachloride). Beforeimmersion, allow the carbon tetrachloride to evaporate for afew minutes. The gain in mass due to the thin film of waxdeposited is negligible. This test method may be effectively

FIG. 1 Diagrammatic Sketch of Apparatus Used to Measure Volume of Specimens by Method B-II

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used on air-dry specimens since thin wax film does not appearto affect shrinkage when the specimen is oven-dried.(Warning—Observe necessary precautions to ensure properventilation when carbon tetrachloride is used.)

8.2.3 Moisture Content—Determine the moisture content(M) of the specimen to permit description of the basis on whichthe specific gravity is computed.

8.2.3.1 Specimen—The entire specimen or a representativesegment may be used for the moisture content determination.Remove all loose particles from the specimen and determinethe initial mass (I) in accordance with 6.2.

8.2.4 Drying—Oven-dry the moisture content specimen toconstant mass in accordance with 6.2 and determine theoven-dry mass (F).

9. METHOD C—FLOTATION TUBE

9.1 Applicability9.1.1 Type of Specimen—This procedure provides a rapid

means for obtaining an approximate specific gravity for anelongated specimen of uniform cross section and knownmoisture content. Estimates of specific gravity to the nearest0.2 can be readily made.

9.2 Procedures9.2.1 Specimen Preparation—The specimen shall be slen-

der and of uniform cross section, preferably about 1 in. (25mm) on a side and 10 in. (254 mm) long. The moisture contentmay be any known value.

9.2.2 Measurement—Place the specimen in a slender cylin-der filled with water and allow it to float in as nearly a verticalposition as possible (Fig. 4). The cylinder diameter shall be butlittle larger than the specimen cross section, and the specimenshall not touch the cylinder wall until immersed as far as it willgo. With the specimen floating in an upright position, quicklymark the water level on the specimen to avoid excessiveabsorption of water by the specimen.

10. METHOD D—FORSTNER BIT

10.1 Applicability10.1.1 Type of Specimen—This procedure is particularly

adaptable for determining the specific gravity of logs, timbers,or any in-place elements from which it would be difficult tosaw a more conventional sample. The Forstner-type bit doesnot have a lead screw, and volume of material can be readilyobtained from the diameter of the bit and the depth of the hole.Care must be taken to collect all of the shavings.

10.2 Procedures10.2.1 Volume—Obtain the volume of specimen material by

boring a hole into the element in question with a Forstner-typebit. The diameter of hole and depth of boring shall be such thatan adequate sample is obtained without damage to the element.Accurately measure the diameter of the bit and depth of thehole. Use these dimensions to calculate the specimen volume.

FIG. 2 Diagrammatic Sketch of Apparatus Used to Measure Volume of Specimens by Method B-III

FIG. 3 Method of Measuring Volume of Elongated SpecimensUsing a Graduated Tube

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10.2.2 Mass—Carefully collect all of the chips obtained byboring and immediately weigh them to determine the initialmass (I).

10.2.3 Moisture Content—Determine the moisture content(M) to permit description of the basis on which the specificgravity is computed.

10.2.4 Drying—Oven-dry the chips to constant mass inaccordance with 6.2 and determine the oven-dry mass (F).

11. METHOD E—INCREMENT CORES

11.1 Applicability11.1.1 This procedure is particularly adaptable for obtaining

specimens to determine the specific gravity of standing treesbut is also suitable for use on logs, poles, piles, or otherstructural elements. Since only a pencil-sized hole is made inthe member in question, it has no material effect on theproperties of the member and can be easily sealed.

11.2 Procedures11.2.1 Volume—Obtain the specimen material by extracting

a core from the member by means of a standard incrementborer. Obtain the volume from the diameter of the cutting edgeof the increment borer and measure the length of the coreimmediately after it is removed from the member. Handle thecore carefully to prevent damage or loss of any portion.

11.2.2 Mass—When the moisture content of the element isdesired, weigh the increment core immediately after the lengthis measured in order to obtain the initial mass (I). If this isimpossible, the core must be protectively wrapped to preventloss of moisture.

11.2.3 Drying—Oven-dry the increment core to constantmass in accordance with 6.2 and determine the oven-dry mass.

12. METHOD F—CHIPS 3

12.1 Applicability12.1.1 This procedure is specifically designed to determine

the specific gravity of wood chips. This is most often obtainedon a green volume, oven-dry mass basis, although otherspecific gravity values can be obtained.

12.2 Procedures12.2.1 Specimen—Select a representative sample of chips

weighing 0.66 to 0.77 lb (approximately 300 to 350 g) for test.Remove sawdust and undersized chips by shaking on athree-mesh sieve.

12.2.2 Mass—Obtain the initial mass (I) of the chips inaccordance with 6.2.

12.2.3 Volume—Submerge the chips in water at room tem-perature for at least 1 h to ensure that they are at their greenvolume and will not absorb water during volume measurement.Then remove them from the water, allow them to drain in awire-mesh basket, and place them in the centrifuge basket.Centrifuge the chips from 800 to 1200 rpm for 1 to 4 min.

12.2.3.1 Place a container holding enough water to freelysubmerge the chip holder on one scale pan and balance it.Submerge the empty chip holder, except for its wire handle, inthe water container. The chip holder must not touch the sides orbottom of the container, and shall be balanced by mass whichrepresent the volume of water equivalent to that of the emptychip holder. Transfer the chips to the chip holder and slowlylower them into the container of water, being careful to removeany entrapped air. Balance the scale and obtain the massnecessary to balance the volume of water equal to the volumeof chips (V).

12.2.4 Drying—Remove the chips and oven-dry to constantmass in accordance with 6.2 to determine the oven-dry mass(F).

13. Calculation

13.1 Moisture Content (M, %)13.1.1 If Test Methods D 4442 are used, the moisture

content is calculated as follows:

M 5 100[~I – F!/F] (1)

where:

I = initial massN = final mass (oven-dry)

13.1.2 If Test Methods D 4444 are used, the moisturecontent is determined from moisture meter readings correctedfor temperature and species. In this case, the final (oven-dry)mass is estimated as follows:

F 5 I/[1 1 0.01M] (2)

where:

3 Additional information on this test method may be obtained from TAPPI 258om-02, Basic Density and Moisture Content of Pulpwood. Available from TAPPI, 15Technology Parkway South, Norcross, GA 30092.

FIG. 4 Cylinder and Specimen Used in Flotation Tube Method ofSpecific Gravity Determination

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I = initial mass,M = moisture content determined by the meter (Test Meth-

ods D 4444).13.2 Specific Gravity (S)13.2.1 For Methods A, B, D, E, and F, specific gravity is

calculated based on oven-dry mass and volume at test using thefollowing formula:

S 5 KF/V (3)

where:

F = final (oven-dry) mass of specimen as determinedin13.1,

V = Ltw, volume of specimen as measured at the time oftest,

L = length of specimen,t = thickness of specimen,w = width of specimen,K = constant whose value is determined by the units used to

measure mass and volume:K = 27.68 when mass is in lb and volume is in in.3,K = 453.59 when mass is in lb and volume is in cm3,K = 453 590 when mass is in lb and volume is in mm3,K = 0.061 when mass is in g and volume is in in.3,K = 1.00 when mass is in lb and volume is in cm3,K = 1000 when mass is in lb and volume is in mm3,

13.2.2 for Method C, specific gravity of the specimen at thegiven moisture content is calculated using the followingformula:

S 5 Li/L/[1 1 M] (4)

where:

Li = immersed length of specimen,L = total length of specimen, andM = moisture content of specimen at the time of test, %

(Note 1)

NOTE 1—The term [1 + 0.01M] accounts for the mass of moisture in thespecimen. For oven-dry specimens it equals unity.

13.3 Conversion of Values—It may often be desirable toconvert the specific gravity obtained at one moisture content to

that at some other moisture content condition. This may beapproximated by the use of the chart in Fig. 5. The values ofspecific gravity based on oven-dry volume or volume at thecurrent moisture content, less than the fiber saturation value,are read on the left-hand scale. The specific gravity valuesbased on green volume are plotted on the diagonal lines. Allvalues are based on oven-dry mass.

13.3.1 To illustrate the use of the chart, assume the specificgravity on an oven-dry mass and green volume basis is 0.55and it is desired to find the specific gravity for a 12 % moisturecontent condition. Enter the chart at the 12 % moisture contentand move vertically to the point where this line intersects the0.55 specific gravity value (between diagonals 0.54 and 0.56)and move horizontally to the left-hand scale to read the specificgravity value 0.60. If the specific gravity on an oven-dry massand volume basis is 0.54 and the specific gravity at 15 %moisture content is desired, enter the chart at 0.54 on theleft-hand scale and move parallel to the diagonals to anintersection with the 15 % moisture content line, then movehorizontally to the left-hand scale to read 0.50. If the specificgravity at 8 % moisture content is 0.45 and the value at 15 %moisture content is desired, enter the chart with 8 % moisturecontent on the lower scale and 0.45 on the left-hand scale; fromthis intersection move parallel to the diagonal lines to anintersection with the 15 % moisture content line and thenhorizontally to the left-hand scale to read 0.44.

14. Report

14.1 Report—The report shall identify the material as com-pletely as possible, the method of selecting test specimens, thetest procedure used, and the conditions under which thevolume and mass were determined.

14.2 The basis for calculating the specific gravity shall beclearly referenced as shown in 13.

15. Precision and Bias

15.1 The precision and bias of these test methods fordetermining specific gravity are being established.

16. Keywords

16.1 specific gravity; wood; wood-based material

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FIG. 5 Relation of Specific Gravity and Moisture Content

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APPENDIXES

(Nonmandatory Information)

X1. CONVERSION FORMULAS FOR SPECIFIC GRAVITY/MOISTURE CONTENT RELATIONSHIPS

X1.1 When a mathematical expression for the conversionof specific gravity values obtained at one moisture content tothat at some other moisture content condition is required, thefollowing formulas may be used:4

X1.1.1 Specific gravity at any moisture content M, belowthe fiber-saturation point, determined from specific gravityvalues based on mass when oven-dry and volume when greenand on mass and volume when oven-dry.

Sa 5 FSd 2 ~S d 2 Sg!M30 G (X1.1)

X1.1.2 Specific gravity (Sa) computed for any moisturecontent M below the fiber-saturation point when the specificgravity of the wood at some particular moisture content isknown or assumed.

(a) based on specific gravity of wood when green = Sg

Sa 5Sg

1 2 Sg ~0.009!~30 2 M!(X1.2)

(b) based on specific gravity of wood when oven-dry = Sd

Sa 5Sd

1 1 S d ~0.009!M (X1.3)

X1.1.3 If M1 is the percent moisture content when thespecific gravity is Sa, M2 is the percent moisture content whenthe specific gravity is Sb and M2 is greater than M1 then

~a! Sa 5Sb

1 2 Sb ~0.009!~M 2 2 M1!(X1.4)

~b! Sb 5Sa

1 1 Sa ~0.009!~M 2 2 M1!(X1.5)

where:M = percentage moisture based on oven-dry mass,Sa and Sb = specific gravity values when wood has mois-

ture content values of M1 and M2 respec-tively, and

Sd = specific gravity based on the mass of theoven- dry wood and volume when oven-dry,and

S g = specific gravity based on the mass of theoven- dry wood and volume when green.

X2. COMMENTARY

X2.1 In previous editions of the standard, there was nodefinition of specific gravity and each method included adifferent calculation section, which made the calculation pro-cedures prone to inconsistencies in interpretation betweendifferent users. To improve the structure of the standard and tominimize ambiguities in calculations, the terminology sectionwas introduced and calculation procedures for all methodswere unified in one calculation section in 200X edition.

X2.2 Specific Gravity—In general, specific gravity of asubstance is the ratio of mass of a unit volume of a material ata stated temperature to the mass of the same volume of gas-freedistilled water at a stated temperature (as shown in TestMethod E 1547). The reference density of gas-free distilledwater at 4°C equals 1.000 g/cm3. In this standard, the mea-surements of mass and volume are allowed to be performed ata room temperature, and pure water to be used in theexperiments. Given the variability of the specific gravity ofwood, the influence of temperature variations between labora-tories can be neglected for most practical applications andconsidered as a part of the precision of the test methods in thisstandard. However, if the purpose of the experiment requireshigher precision, the reference temperature at the time of testshould be considered and distilled water should be used.

X2.3 The specific gravity of wood is based on the oven-drymass, but the volume may be that in the green, air-dry or

oven-dry condition depending on the purpose of the experi-ment. Specific gravity determined using oven-dry mass andgreen volume is referred to as basic specific gravity. The basicspecific gravity is often used in silvicultural studies to charac-terize specific gravity of species. For example, basic specificgravity data for commercial species of woods grown in theUnited States and Canada are given in Practice D 2555.Adjustments of moisture meters for wood species are com-monly based on specific gravity determined on the oven-drymass and the volume at the 12% moisture content. Specificgravity data in Wood Handbook6 are reported on both the 12%volume and green volume bases. Design specifications forwood, such as contained in the National Design Specificationfor Wood Construction and CSA O86, are based on oven-drymass and oven-dry volume. Approximate conversions betweenvalues of specific gravity obtained at different moisture con-tents can be done using the chart in Fig. 5 (14) or formulas inAppendix X1.

X2.4 Report—Many other standards make references toTest Methods D 2395 for determining specific gravity. Sincethis standard allows for determining specific gravity at variousmoisture contents, it is important that the basis and method forcalculating the values of specific gravity is always stated in thereport.

4 Simpson, W. T., “Specific Gravity, Moisture Content, and Density Relationshipfor Wood,” USDA Forest Service, Forest Products Laboratory General TechnicalReport FPL-GTR-76.

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