ASTM D661-93
(Test Method)Standard Test Method for Evaluating Degree of Cracking of Exterior Paints
Standard Test Method for Evaluating Degree of Cracking of Exterior Paints
SCOPE
1.1 This test method covers the evaluation of the degree of cracking of exterior paints by comparison with photographic standards.
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Designation: D 661 – 93
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
1
Evaluating Degree of Cracking of Exterior Paints
This standard is issued under the fixed designation D 661; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope are generally arranged in parallel lines, usually either horizon-
tally or vertically, over the surface of the film. These breaks
1.1 This test method covers the evaluation of the degree of
often follow the line of brush marks.
cracking of exterior paints by comparison with photographic
5.1.3 Sigmoid Type—Cracking in which the breaks in the
standards.
film form a pattern consisting of curves meeting and intersect-
2. Referenced Documents
ing, usually on a relatively large scale.
2.1 ASTM Standards:
6. Use of Photographic Reference Standards
D 660 Test Method for Evaluating Degree of Checking of
2 6.1 The photographic reference standards that are part of
Exterior Paints
this test method and are provided in the Pictorial Standards of
2.2 Other Standards:
3 Coating Defects Handbook are representative of the degree of
Pictorial Standards of Coating Defects Handbook
cracking of exterior paint films. Fig. 1 and Figures 2 are for
3. Terminology illustration purposes only and should not be used for evalua-
tion.
3.1 Definitions:
3
6.2 The use of the photographic reference standards illus-
3.1.1 cracking—that phenomenon manifested in paint films
trated in Fig. 1 requires the following precautions:
by a break extending through to the surface painted. Where this
6.2.1 The accompanying photographic reference standards
is difficult to determine, the break should be called a crack only
show line-type cracking only. Irregular and sigmoid-type
if the underlying surface is visible. The use of a magnification
cracking may also be interpreted from these photographs.
of 10 diameters is recommended in cases where it is difficult to
6.2.2 Care must be taken not to confuse various types of
differentiate between cracking and checking (see Test Method
failure that may be present on the same surface. This is
D 660).
particularly true in observing cracking and checking. Cracking
4. Significance and Use
may very often be an advanced stage of checking and is very
often in evidence along with checking and other failures.
4.1 Cracking failure of paint films can occur in use. This test
6.2.3 It must be realized that the degree of failure will vary
method provides a means of evaluating the degree of the failure
over any given area. Therefore, an average portion of the film
by comparing the pictorial stan
...
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