ASTM_D_4941_-_06_2010.pdf

Designation:D494106(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 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 practice covers the production of uniform films ofartists tube paints and other nonflowing pigmented paintsusing paint applicators 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 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 Paint,Related Coatings,Materials,andApplicationsD4838 Test Method for Determining the Relative TintingStrength of Chromatic PaintsE1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation3.Terminology3.1 DefinitionsSee Terminology D16 for definitions ofterms used in this practice.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 for the evaluation of paint charac-teristics.3.2.2 drawdown bar,na metal applicator with a specifiedgap designed to deposit a wet paint film uniformly on aspecified test 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 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 artists 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 difference 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 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 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 7.61This practice is under the jurisdiction of ASTM Committee 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 D4941 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 cm(3 in.)and 15.2 cm(6 in.).The second 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.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 using two spatulas.Tubepaints that have separated should be expelled completely andmixed.NOTE1The 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