1、Designation: D4838 88 (Reapproved 2016)Standard Test Method forDetermining the Relative Tinting Strength of ChromaticPaints1This standard is issued under the fixed designation D4838; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the determination of theabsorption tinting strength of a chromatic test paint r
3、elative tothat of a standard or reference paint of the same chemical type.The procedures are based on dilution of the paints with astandard mixing white paint, followed by instrumental mea-surement and calculation. Provision is made for correcting theresults for small differences in hue or chroma, o
4、r both, betweenthe test and reference chromatic paints.1.2 This test method is intended for the comparison ofpaints containing the same type of vehicle (acrylic, alkyd, oroil) and single-pigment colorants of the same Colour Index2name and number. The amounts of the pigment and of the othercomponents
5、 of the paint need not be known.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user o
6、f this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1640 Test Methods for Drying, Curing, or Film Formationof Organic CoatingsD4303 Test Methods for Lightfastness of
7、Colorants Used inArtists MaterialsE284 Terminology of AppearanceE308 Practice for Computing the Colors of Objects by Usingthe CIE SystemE1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation3. Terminology3.1 Definitions:3.1.1 tinting strength, nmeasure of the effectiveness withw
8、hich a unit quantity of a colorant alters the color of a material.For scattering and absorbing colorants (pigments), both ab-sorption and scattering tinting strength must be specified.3.1.2 tinting strength, absorption, nrelative change in theabsorption properties of a standard white material when a
9、specified amount of an absorbing pigment, black or chromatic,is added to it.3.1.2.1 DiscussionThis is the common definition of tint-ing strength; however, this definition of the term can bemisleading. For example, the tinting strength of a yellowcolorant depends on its scattering as well as its abso
10、rption. Itstinting strength as determined from a mixture with whiteprovides no information about its behavior when mixed withlow-scattering colorants, such as a black.3.1.3 tinting strength, scattering, nrelative change in thescattering properties of a standard black material (with nowhite pigment p
11、resent) when a specified amount of a white orchromatic scattering pigment is added to it.3.1.4 For other definitions, see Terminology E284.3.2 Definitions of Terms Specific to This Standard:3.2.1 drawdown, na layer of paint deposited on a substrateby use of a drawdown bar to evaluate the characteris
12、tics of thepaint.3.2.2 drawdown bar, na bar designed to deposit a speci-fied thickness of wet paint film uniformly on a specified testpanel or other substrate.4. Summary of Test Method4.1 Chromatic paints are diluted with white paint to obtainmixtures that will produce a drawdown having 35 to 45 %re
13、flectance factor at the wavelength of maximum absorption.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.57 on Artist Paints and Related Materials.Current edition approved
14、July 1, 2016. Published July 2016. Originally approvedin 1988. Last previous edition approved in 2010 as D4838 88 (2010). DOI:10.1520/D4838-88R16.2Colour Index, The Society of Dyers and Colourists, London, 1987. Availablefrom the American Association of Textile Chemists and Colorists, P.O. Box 12215
15、,Research Triangle Park, NC 27709.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM Internationa
16、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 Drawdowns of these mixture paints are produced atcomplete hiding.4.3 The drawdowns are measured to obtain tristimulus filterreadings R, G, B either directly or by computation from CIEtristimulus values X, Y, Z
17、.4.4 One of the samples is designated the standard, and thepercents of tinting strength, % TS, of the others are calculatedrelative to that of the standard. Provision is made for correctingthis tinting strength for small differences in hue, chroma, orboth, between the standard and the test specimen,
18、 and forobtaining an average tinting strength and a range.5. Significance and Use5.1 Tinting strength may be one factor in judging therelative economic value of paints, since pigment concentrationcontributes to strength in a major way; other factors areformulation and color development in grinding.
19、The user mayalso select products for other properties, such as transparency,that are accompanied by different tinting strengths. The resultsof this test method may be used for production control orquality comparisons.5.2 The product with the greatest or the least tinting strengthmay not be the most
20、desirable for a given artistic use. Forexample, low tinting strength may lead to the need to use anexcessively high pigment concentration to obtain a desiredcolor effect, and this may lead to defects in the dry paint film.5.3 This test method applies only to single-pigment paints.The tinting strengt
21、h of paints that contain two or morechromatic pigments with different optical properties cannot beevaluated by this test method.5.4 The term “similar chemical type” used in 1.1 does notlimit the ingredients in the paints to identity, but refers tocompatibility in the case of vehicles and to similari
22、ty in thecase of pigment types.5.5 While the instrumental evaluation of tinting strength isdescribed, visual comparisons can also be used, with lowerprecision, and should be made to provide confirmation of theinstrumental and computational results.5.6 If the sample and standard are widely different
23、inappearance when prepared at the same ratio of chromatic towhite paint, another sample should be prepared to bring thetwo closer in appearance, to obtain the most accurate results.5.7 The quantities of chromatic and white paints mixedmust be accurately known, on either a weight or a volumebasis, bu
24、t the concentration of pigment in the chromatic paintneed not be known.5.8 When the paints being compared have the same vehicleand pigment (same Colour Index name and number) the valuesof uncorrected tinting strength from 9.1 and corrected tintingstrength from 9.2 should be nearly the same. If they
25、are not, anaverage of the two tinting strengths is recommended as the bestestimate of the true value, and a range provides a measure ofthe magnitude of the uncertainty, which is due to differences inhue or chroma, or both, between the paints.5.9 Strictly speaking, the Kubelka-Munk-type analysis ofth
26、is test method should not be applied to the tristimulus filterreadings used, but only to spectral data. For the purposes of therelative comparisons of this test method, however, the errorsintroduced by the calculations used cancel to an adequatedegree.6. Apparatus and Materials6.1 Laboratory Balance
27、, top-loading, having a sensitivity of0.01 g.6.2 Drawdown bars, capable of producing smooth paintfilms with wet-film thicknesses between 0.075 and 0.25 mm(0.003 and 0.010 in.).6.3 Opacity charts, sealed-paper type with black and whiteareas.6.4 Color-Measuring Instrument, either a spectrophotom-eter
28、providing 1931 CIE tristimulus values X, Y, Z for CIEstandard illuminant C, or a tristimulus colorimeter providingeither such tristimulus values or colorimeter readings R, G, B.6.5 Mixing White Paint, prepared as described in the Speci-men Preparation, Mixing Whites for Dilution of Colors sectionof
29、Test Methods D4303. Alternatively, a commercial titanium-dioxide white artists paint may be used. The mixing whitepaint must be made with the same vehicle type (acrylic, alkyd,or oil) as the paints to be tested.7. Specimen Preparation7.1 Obtain representative samples of the chromatic paints tobe tes
30、ted. For tube paints, expel the entire contents of the tubeand mix thoroughly before sampling.7.2 Determine the approximate amount of chromatic paintto be added to 20 g of mixing white paint to obtain a drawdownwith 35 to 45 % reflectance factor at the wavelength ofmaximum absorption. If the amount
31、of chromatic paint is notknown in advance, consult the table in Appendix X1. Forpigments other than those listed, use as the general guidelinethe addition of5gofchromatic paint containing an inorganicpigment or1gofchromatic paint containing an organicpigment to the 20 g of mixing white paint.NOTE 1A
32、ppendix X1 of Test Methods D4303 describes a method forcomputing the necessary adjustments in quantities required if additionaltrials are needed to obtain the desired level of reflectance factor.7.3 Weigh out the chromatic and mixing white paints to thenearest 0.01 g, and mix thoroughly.7.4 Prepare
33、drawdowns by placing the paint mixture at oneend of an opacity chart and pulling the drawdown bar smoothlythrough the paint and across the chart. Paste paints should bespread with a spatula or palette knife over the entire chart areato be covered before pulling the bar down the chart.7.5 Allow the d
34、rawdowns to reach the dry-to-touch time asdescribed in the Procedure section of Test Methods D1640.Acrylic paints should dry in air overnight. Alkyd paints mayrequire 5 days to dry. Oil paints may require 2 months to dry.7.6 Determine whether each drawdown is at completehiding by measuring the porti
35、ons of it over the black and overD4838 88 (2016)2the white areas of the chart to determine tristimulus value Y orcolorimeter reading G. If the quotient YB/YWor GB/GW, wherethe subscripts refer to measurements over black and white,respectively, is greater than 0.98, the drawdown can beconsidered at c
36、omplete hiding. If the drawdown is not atcomplete hiding, prepare a thicker drawdown or a drawdownmade with multiple coats of paint, one over another.NOTE 2At the required dilution with white, a drawdown bar with anaperture of 0.15 mm (0.006 in.) will usually make a drawdown atcomplete hiding. In th
37、e cases of some acrylic paints and a few oil paintsit may be necessary to increase the aperture to 0.25 mm (0.010 in. ) toobtain complete hiding. If this leads to a slow-drying film or a film that iswrinkled when dry, multiple coats can be applied by depositing a second0.15 mm (0.006 in.) coat, draw
38、ing down at a right angle to the first coat.After this coat dries, a third coat can be applied if necessary by using ashorter bar that rides over the previous coats.8. Procedure8.1 Obtain values of R, G, B for each sample by either of thetwo following procedures.8.1.1 Measure the drawdown with a spe
39、ctrophotometer or atristimulus colorimeter to determine 1931 CIE tristimulusvalues X, Y, Z for CIE standard illuminant C. Follow PracticeE1164 and Practice E308. If hemispherical (integrating-sphere)geometry is used, measure with the specular componentexcluded.8.1.2 If a colorimeter that is direct r
40、eading in R, G, B isused, measure these quantities.8.2 If X, Y, Z are measured, calculate R, G, B by use of thefollowing equations:R 5 X/0.98 2 0.2Z/1.18!/0.8 (1)G 5 Y (2)B 5 Z/1.18 (3)NOTE 3The use of the 1931 CIE system (and standard observer) andstandard illuminant C is specified because all know
41、n tristimulus colorim-eters that are direct reading in R, G, B measure for these conditions. Ifvalues of X, Y, Z are obtained by spectrophotometry, the 1964 CIE systemand other CIE standard illuminants may be used. Eq 1-3 are specific to theconditions, and must be replaced by the appropriate equatio
42、ns if otherconditions are specified.4The article referenced also discusses correctingthe measured values for surface reflections.9. Calculation9.1 Calculate uncorrected relative tinting strength, % TSUCas follows:9.1.1 Using decimal-fraction values of R, G, B, calculateKubelka-Munk-type ratios of ab
43、sorption coefficient, K,toscattering coefficient, S:K/S!R5 1 2 R!2/2R (4)K/S!G5 1 2 G!2/2G (5)K/S!B5 1 2 B!2/2B (6)9.1.2 Calculate the pigment concentration term CP:CP5 Qc/Qc1Qw! (7)where:Qc= quantity of chromatic paint, g,Qw= quantity of white paint, g.NOTE 4If it is desirable to use volume rather
44、than weight as the basisfor comparison of tinting strengths, determine the densities of the paintsand compute the volumes of the weighed samples. Calculate CPby use ofEq 7 using volumes instead of weights.9.1.3 Calculate normalized values of (K/S), denoted N,asfollows:NR5 K/S!R/CP(8)NG5 K/S!G/CP(9)N
45、B5 K/S!B/CP(10)9.1.4 Select one of the specimens to be denoted the standardand assigned the value of 100 % tinting strength. The tintingstrength of the remaining specimens will be determined rela-tive to that of the standard.9.1.5 Select the value of N to be used in the calculation of% TSUCby one of
46、 the following three methods:9.1.5.1 Select N based on the visually determined color ofthe specimen: For blue and green specimens, select NR; forpurple and red specimens, select NG; and for yellow and orangespecimens, select NB. Relabel the selected value N1SPECandNSTDfor the specimens and the stand
47、ard, respectively. Relabelthe remaining two values of N as N2SPECand N3SPECfor thespecimens and N2STDand N3STDfor the standard.9.1.5.2 If the specimen color cannot be classified accuratelyin 9.1.5.1, select the lowest value of N as N1. The sameselection must be made for the standard and all specimen
48、s to becompared. Relabel the values of N as in 9.1.5.1.9.1.5.3 If the values of NRand NBfor the specimen are bothlow and approximately equal, follow the procedure in AnnexA1 to select N and calculate the tinting strength.9.1.6 Calculate % TSUCas follows:% TSUC5 100N1SPEC/N1STD! (11)9.2 Calculate tin
49、ting strength corrected for differences inhue and chroma, % TSC, by use of the following equations:dSPEC5 N2SPEC1N3SPEC(12)dSTD5 N2STD1N3STD(13)D 5 dSPEC2 dSTD!/2 (14)% TSC5 100 N1SPEC2 D!/N1STD(15)9.3 Calculate average tinting strength, % TSAV, and range Eas follows:% TSAV5 % TSUC1% TSC!/2 (16)E 56% TSUC2 % TSC!/2 (17)10. Report10.1 Report the following information:10.1.1 Complete identification of the specimens, includingbrand and color name, date of manufacture, and lot number ifavailable.10.1.2 Name of color-measuring instrument used, methodof standar
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