1、Designation: D4941 06 (Reapproved 2010)Standard Practice forPreparing Drawdowns of Artists Paste Paints1This standard is issued under the fixed designation D4941; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. 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 practice covers the production of uniform films ofartists tube paints and other nonflowing pigmented paintsusing paint ap
3、plicators designed for less viscous paints.1.2 Information on how to achieve opaque specimens fromthese paints is included.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
4、 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 Documents2.1 ASTM Standards:2D16 Terminology for Pain
5、t, Related Coatings, Materials,and ApplicationsD4838 Test Method for Determining the Relative TintingStrength of Chromatic PaintsE1164 Practice for Obtaining Spectrometric Data forObject-Color Evaluation3. Terminology3.1 DefinitionsSee Terminology D16 for definitions ofterms used in this practice.3.
6、2 Definitions of Terms Specific to This Standard:3.2.1 drawdown, na layer of paint deposited on a sub-strate by use of a drawdown bar for the evaluation of paintcharacteristics.3.2.2 drawdown bar, na metal applicator with a specifiedgap designed to deposit a wet paint film uniformly on aspecified te
7、st panel (for example, an opacity chart) or othersubstrate.4. Summary of Practice4.1 The paint is spread over the area of the test panel to becovered by the drawdown and the bar is pulled down withpressure just sufficient to avoid lifting of the bar from the chartsurface.4.2 Test panels are allowed
8、to dry in a dust-free environ-ment.4.3 If complete hiding (opacity) is needed and not producedby a single paint film, a second film is applied at a 90 angle tothe first. If required, additional layers may be applied using anarrower drawdown bar.5. Significance and Use5.1 Quality standards for artist
9、s paints require the evalua-tion of various appearance characteristics of paint films.Tinting strength determination (Test Method D4838) specifi-cally requires the preparation of drawdowns for colorimetricmeasurement. Other evaluations such as color designation,transparency, gloss, and color differe
10、nce measurements alsorequire drawdown samples.5.2 Artists tube paints have a paste consistency that makesthe use of traditional film application methods difficult, espe-cially for drying oil paints.5.3 Artists paints vary in two properties important to thepreparation of films, that is, transparency
11、and drying time.Colorimetric determination and some other types of evaluationrequire paint specimens that completely hide the substrate.Very transparent paints require such a thick film to producecomplete hiding that drying times is excessively long or thespecimen surface is blemished. When complete
12、 hiding isnecessary, this practice is designed to provide opaque filmswithout these defects through application of a series of thinfilms.6. Apparatus6.1 Drawdown Bars, two, of different widths with a clear-ance of 0.152 mm (0.006 in.). Recommended widths are 7.6cm (3 in.) and 15.2 cm (6 in.). The se
13、cond bar is required toprepare drawdowns with more than two layers. Wire wounddrawdown bars have been found to be unsuitable.6.2 Drawdown Charts, sealed paper type, half black andhalf white if transparency is being evaluated or opacity isnecessary.1This practice is under the jurisdiction of ASTM Com
14、mittee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.57 on Artist Paints and Related Materials.Current edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1989. Last previous edition approved in 2006 as D49
15、41 06. DOI:10.1520/D4941-06R10.2For 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.1Copyright ASTM International,
16、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Procedure7.1 Attach chart to a firm, smooth, level plane surface usingtape, a vacuum plate, or a clamp. Label the chart with theidentity of the specimen and other data as required.7.2 Mix paint sample thoroughly
17、using two spatulas. Tubepaints that have separated should be expelled completely andmixed.NOTE 1The use of coated freezer wrapping paper as a mixing surfacesimplifies clean up. The same paper can be used for weighing specimenswhen required as in the tinting strength determination (Test MethodD4838).
18、7.3 Using a spatula, spread the paint, in a thickness exceed-ing the bars gap clearance, over the entire area to be coveredby the drawdown. Do not cover the area to be contacted by thesupporting feet of the wider of the two bars. Starting at the topof the chart and using the wider bar, draw the bar
19、down overthe paint in an even motion applying sufficient pressure toensure that the resistance of the viscous paint does not raise thefeet of the bar from the surface. When using oil paints themotion should be slow enough to allow for the high viscosity.Acrylic paints, which have short drying times,
20、 should beapplied immediately after mixing to avoid premature filmformation.7.4 After drying in a horizontal position for 15 min,specimens may be hung in a vertical position in a dust-free areato complete the drying. Allow 24 h for acrylic and alkyd paintsand 48 h or longer for oil paints until dry
21、to touch.7.5 Examine the specimen for surface defects and discard ifunacceptable.7.6 If complete hiding is required, compare, either visuallyor instrumentally, the lightness of the paint on the black portionof the chart with that on the white. For instrumental evaluation,follow the procedures given
22、in Practice E1164 to determineCIE Y for each portion, then calculate the contrast ratio of thepaint film on the two portions of the chart (CIE Yblack/CIEYwhite). A contrast ratio of 0.98 or higher is considered opaque.7.6.1 If opacity is not sufficient, rotate the chart through a90 angle and deposit
23、 a second film using the wider bar torepeat the procedure in 7.3 through 7.5. If additional layers arerequired, repeat this sequence using the narrower bar. Becareful each time that the feet of the drawdown bar ride on thesurface of the combined lower layers. See Fig. 1 and Fig. 2.NOTE 2The most tra
24、nsparent paints studied were found to requirethree coats; however, in some instances, such as with alizarin crimson oilpaint, it may not be practical to obtain complete hiding.8. Keywords8.1 artists paint; drawdown; paint specimensFIG. 1 Preparation for DrawdownFIG. 2 Three Overlapping DrawdownsD494
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28、ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D4941 06 (2010)3
