ASTM D661-93(2019)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D661 − 93 (Reapproved 2019)
Standard Test Method for
Evaluating Degree of Cracking of Exterior Paints
This standard is issued under the fixed designation D661; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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. Scope 4. Significance and Use
1.1 This test method covers the evaluation of the degree of 4.1 Cracking failure of paint films can occur in use.This test
cracking of exterior paints by comparison with photographic methodprovidesameansofevaluatingthedegreeofthefailure
standards. by comparing the pictorial standards.
1.2 This international standard was developed in accor-
5. Types of Cracking
dance with internationally recognized principles on standard-
5.1 Three types of cracking are recognized:
ization established in the Decision on Principles for the
5.1.1 Irregular Pattern Type—Cracking in which the breaks
Development of International Standards, Guides and Recom-
in the film are in no definite pattern.
mendations issued by the World Trade Organization Technical
5.1.2 Line Type—Cracking in which the breaks in the film
Barriers to Trade (TBT) Committee.
are generally arranged in parallel lines, usually either horizon-
2. Referenced Documents tally or vertically, over the surface of the film. These breaks
2 often follow the line of brush marks.
2.1 ASTM Standards:
5.1.3 Sigmoid Type—Cracking in which the breaks in the
D660 Test Method for Evaluating Degree of Checking of
film form a pattern consisting of curves meeting and
Exterior Paints
intersecting, usually on a relatively large scale.
2.2 Other Standards:
Pictorial Standards of Coating Defects Handbook
6. Use of Photographic Reference Standards
6.1 The photographic reference standards that are part of
3. Terminology
this test method and are provided in the Pictorial Standards of
3.1 Definitions of Terms Specific to This Standard:
Coating Defects Handbook are representative of the degree of
3.1.1 cracking, n—that phenomenon manifested in paint
cracking of exterior paint films. Fig. 1 is for illustration
films by a break extending through to the surface painted.
purposes only and should not be used for evaluation.
3.1.1.1 Discussion—Where this is difficult to determine, the
6.2 The use of the photographic reference standards illus-
break should be called a crack only if the underlying surface is
trated in Fig. 1 requires the following precautions:
visible. The use of a magnification of 10 diameters is recom-
6.2.1 The accompanying photographic reference standards
mended in cases where it is difficult to differentiate between
show line-type cracking only. Irregular and sigmoid-type
cracking and checking (see Test Method D660).
cracking may also be interpreted from these photographs.
6.2.2 Care must be taken not to confuse various types of
failure that may be present on the same surface. This is
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of particularly true in observing cracking and checking. Cracking
Subcommittee D01.25 on Evaluation of Weathering Effects.
may very often be an advanced stage of checking and is very
Current edition approved Oct. 1, 2019. Published October
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