ASTM_D_661_-_93_2019.pdf

Designation:D66193(Reapproved 2019)Standard Test Method forEvaluating Degree of Cracking of Exterior Paints1This standard is issued under the fixed designation D661;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers the evaluation of the degree ofcracking of exterior paints by comparison with photographicstandards.1.2 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D660 Test Method for Evaluating Degree of Checking ofExterior Paints2.2 Other Standards:Pictorial Standards of Coating Defects Handbook33.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cracking,nthat phenomenon manifested in paintfilms by a break extending through to the surface painted.3.1.1.1 DiscussionWhere this is difficult to determine,thebreak should be called a crack only if the underlying surface isvisible.The use of a magnification of 10 diameters is recom-mended in cases where it is difficult to differentiate betweencracking and checking(see Test Method D660).4.Significance and Use4.1 Cracking failure of paint films can occur in use.This testmethod provides a means of evaluating the degree of the failureby comparing the pictorial standards.5.Types of Cracking5.1 Three types of cracking are recognized:5.1.1 Irregular Pattern TypeCracking in which the breaksin the film are in no definite pattern.5.1.2 Line TypeCracking in which the breaks in the filmare generally arranged in parallel lines,usually either horizon-tally or vertically,over the surface of the film.These breaksoften follow the line of brush marks.5.1.3 Sigmoid TypeCracking in which the breaks in thefilm form a pattern consisting of curves meeting andintersecting,usually on a relatively large scale.6.Use of Photographic Reference Standards6.1 The photographic reference standards that are part ofthis test method and are provided in the Pictorial Standards ofCoating Defects Handbook are representative of the degree ofcracking of exterior paint films.Fig.1 is for illustrationpurposes only and should not be used for evaluation.6.2 The use of the photographic reference standards3illus-trated in Fig.1 requires the following precautions:6.2.1 The accompanying photographic reference standardsshow line-type cracking only.Irregular and sigmoid-typecracking may also be interpreted from these photographs.6.2.2 Care must be taken not to confuse various types offailure that may be present on the same surface.This isparticularly true in observing cracking and checking.Crackingmay very often be an advanced stage of checking and is veryoften in evidence along with checking and other failures.6.2.3 It must be realized that the degree of failure will varyover any given area.Therefore,an average portion of the filmshould be used for comparison.On larger surfaces it isrecommended that ratings be made at several locations and themean and range reported.6.2.4 Paint films may collect excessive quantities of dirt,which may mask the type and degree of failure.If necessary,dirt should be removed by careful and gentle brushing with amoderately soft brush.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.25 on Evaluation of Weathering Effects.Current edition approved Oct.1,2019.Published October 2019.Originallyapproved in 1942.Last previous edition approved in 2011 as D661 93(2011).DOI:10.1520/D0661-93R19.2For 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.3Copies of the pictorial photographic reference standards are contained in thepublication Pictorial Standards of Coatings Defects and may be obtained from theFederation of Societies for Coatings Technology,492 Norristown Rd.,Blue Bell,PA 19422.The silver halide-gelatin photographs are intended to be the only primaryreference standards for this method.The reproductions of them in this test methodare for the purpose of illustration only.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the