1、Designation: D 4838 88 (Reapproved 2003)Standard Test Method forDetermining the Relative Tinting Strength of ChromaticPaints1This standard is issued under the fixed designation D 4838; 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 (e) 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 pain
3、t relative 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
4、, or 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 othercompone
5、nts 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 use
6、r of 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:D 1640 Test Methods for Drying, Curing, or Film Forma-tion of Organic Coatings at Room Temperature3D 4303 Test Me
7、thods for Lightfastness of Pigments Used inArtists Paints4E 284 Terminology of Appearance3E 308 Practice for Computing the Colors of Objects byUsing the CIE System3E 1164 Practice for Obtaining Spectrophotometric Data forObject-Color Evaluation33. Terminology3.1 Definitions:3.1.1 tinting strengthmea
8、sure of the effectiveness withwhich 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, absorptionrelative change in theabsorption properties of a st
9、andard white material when aspecified 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 sc
10、attering as well as its absorption. 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, scatteringrelative change in thescattering properties of a standard black materia
11、l (with nowhite pigment present) when a specified amount of a white orchromatic scattering pigment is added to it.3.1.4 For other definitions, see Terminology E 284.3.2 Definitions of Terms Specific to This Standard:3.2.1 drawdowna layer of paint deposited on a substrateby use of a drawdown bar to e
12、valuate the characteristics of thepaint.3.2.2 drawdown bara bar designed to deposit a specifiedthickness of wet paint film uniformly on a specified test panelor other substrate.4. Summary of Test Method4.1 Chromatic paints are diluted with white paint to obtainmixtures that will produce a drawdown h
13、aving 35 to 45 %reflectance factor at the wavelength of maximum absorption.4.2 Drawdowns of these mixture paints are produced atcomplete hiding.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility
14、 ofSubcommittee D01.57 on Artist Paints and Related Materials.Current edition approved May 10, 2003. Published June 2003. Originallyapproved in 1988. Last previous edition approved in 1988 as D 4838 - 88 (1998).2Colour Index, The Society of Dyers and Colourists, London, 1987. Availablefrom the Ameri
15、can Association of Textile Chemists and Colorists, P.O. Box 12215,Research Triangle Park, NC 27709.3Annual Book of ASTM Standards, Vol 06.01.4Annual Book of ASTM Standards, Vol 06.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.
16、3 The drawdowns are measured to obtain tristimulus filterreadings R, G, B either directly or by computation from CIEtristimulus values X, Y, Z.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. P
17、rovision is made for correctingthis tinting strength for small differences in hue, chroma, orboth, between the standard and the test specimen, 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
18、of paints, since pigment concentrationcontributes to strength in a major way; other factors areformulation and color development in grinding. The user mayalso select products for other properties, such as transparency,that are accompanied by different tinting strengths. The resultsof this test metho
19、d may be used for production control orquality comparisons.5.2 The product with the greatest or the least tinting strengthmay not be the most desirable for a given artistic use. Forexample, low tinting strength may lead to the need to use anexcessively high pigment concentration to obtain a desiredc
20、olor 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 strength of paints that contain two or morechromatic pigments with different optical properties cannot beevaluated by this test method.5.4 The term “similar chemical
21、 type” used in 1.1 does notlimit the ingredients in the paints to identity, but refers tocompatibility in the case of vehicles and to similarity in thecase of pigment types.5.5 While the instrumental evaluation of tinting strength isdescribed, visual comparisons can also be used, with lowerprecision
22、, and should be made to provide confirmation of theinstrumental and computational results.5.6 If the sample and standard are widely different 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
23、 most accurate results.5.7 The quantities of chromatic and white paints mixedmust be accurately known, on either a weight or a volumebasis, but 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
24、name and number) the valuesof uncorrected tinting strength from 9.1 and corrected tintingstrength from 9.2 should be nearly the same. If they 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 un
25、certainty, which is due to differences inhue or chroma, or both, between the paints.5.9 Strictly speaking, the Kubelka-Munk-type analysis ofthis test method should not be applied to the tristimulus filterreadings used, but only to spectral data. For the purposes of therelative comparisons of this te
26、st method, however, the errorsintroduced by the calculations used cancel to an adequatedegree.6. Apparatus and Materials6.1 Laboratory Balance, 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(0.0
27、03 and 0.010 in.).6.3 Opacity charts, sealed-paper type with black and whiteareas.6.4 Color-Measuring Instrument, either a spectrophotom-eter providing 1931 CIE tristimulus values X, Y, Z for CIEstandard illuminant C, or a tristimulus colorimeter providingeither such tristimulus values or colorimete
28、r readings R, G, B.6.5 Mixing White Paint, prepared as described in the Speci-men Preparation, Mixing Whites for Dilution of Colors sectionof Test Methods D 4303. Alternatively, a commercial titanium-dioxide white artists paint may be used. The mixing whitepaint must be made with the same vehicle ty
29、pe (acrylic, alkyd,or oil) as the paints to be tested.7. Specimen Preparation7.1 Obtain representative samples of the chromatic paints tobe tested. For tube paints, expel the entire contents of the tubeand mix thoroughly before sampling.7.2 Determine the approximate amount of chromatic paintto be ad
30、ded to 20 g of mixing white paint to obtain a drawdownwith 35 to 45 % reflectance factor at the wavelength ofmaximum absorption. If the amount of chromatic paint is notknown in advance, consult the tables in Appendix X1. Forpigments other than those listed, use as the general guidelinethe addition o
31、f5gofchromatic paint containing an inorganicpigment or1gofchromatic paint containing an organicpigment to the 20 g of mixing white paint.NOTE 1Appendix X1 of Test Methods D 4303 describes a method forcomputing the necessary adjustments in quantities required if additionaltrials are needed to obtain
32、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 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 pai
33、nts 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 drawdowns to reach the dry-to-touch time asdescribed in the Procedure section of Test Methods D 1640.Acrylic paints should dry in air overnight. Alkyd paint
34、s 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 portions of it over the black and overthe white areas of the chart to determine tristimulus value Y orcolorimeter reading G. If the quotient YB/YWor GB/GW, whe
35、rethe subscripts refer to measurements over black and white,respectively, is greater than 0.98, the drawdown can beconsidered at complete 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 require
36、d dilution with white, a drawdown bar with anaperture of 0.15 mm (0.006 in.) will usually make a drawdown atcomplete hiding. In the cases of some acrylic paints and a few oil paintsD 4838 88 (2003)2it may be necessary to increase the aperture to 0.25 mm (0.010 in. ) toobtain complete hiding. If this
37、 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, drawing 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 pre
38、vious 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 spectrophotometer or atristimulus colorimeter to determine 1931 CIE tristimulusvalues X, Y, Z for CIE standard illuminant C. Follow PracticeE 1164 and Pract
39、ice E 308. If hemispherical (integrating-sphere) geometry is used, measure with the specular compo-nent excluded.8.1.2 If a colorimeter that is direct reading 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
40、/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 known tristimulus colorim-eters that are direct reading in R, G, B measure for these conditions. Ifvalues of X, Y, Z are obtained by spectrophotometry,
41、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 equations if otherconditions are specified.5The article referenced also discusses correctingthe measured values for surface reflections.9. Calculation9.1 C
42、alculate uncorrected relative tinting strength, % TSUCas follows:9.1.1 Using decimal-fraction values of R, G, B, calculateKubelka-Munk-type ratios of absorption 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 conce
43、ntration term CP:CP5 Qc/Qc1 Qw! (7)where:Qc= quantity of chromatic paint, g,Qw= quantity of white paint, g.NOTE 4If it is desirable to use volume rather than weight as the basisfor comparison of tinting strengths, determine the densities of the paintsand compute the volumes of the weighed samples. C
44、alculate 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)NB5 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
45、 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 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; forpu
46、rple and red specimens, select NG; and for yellow and orangespecimens, select NB. Relabel the selected value N1SPECandNSTDfor the specimens and the standard, respectively. Relabelthe remaining two values of N as N2SPECand N3SPECfor thespecimens and N2STDand N3STDfor the standard.9.1.5.2 If the speci
47、men 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 specimens 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, follo
48、w the procedure in AnnexA1 to select N and calculate the tinting strength.9.1.6 Calculate % TSUCas follows:% TSUC5 100 N1SPEC/N1STD! (11)9.2 Calculate tinting strength corrected for differences inhue and chroma, % TSC, by use of the following equations:dSPEC5 N2SPEC1 N3SPEC(12)dSTD5 N2STD1 N3STD(13)
49、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 standardization, and other information required in theReport section of Practice E 1164 and Practice E 308.10.1.3 Date of test.10.1.4 Test results for % TS
