ASTM D661-93(2000)
(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:D661–93 (Reapproved 2000)
Standard Test Method for
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 5.1.2 Line Type—Cracking in which the breaks in the film
are generally arranged in parallel lines, usually either horizon-
1.1 This test method covers the evaluation of the degree of
tally or vertically, over the surface of the film. These breaks
cracking of exterior paints by comparison with photographic
often follow the line of brush marks.
standards.
5.1.3 Sigmoid Type—Cracking in which the breaks in the
2. Referenced Documents film form a pattern consisting of curves meeting and intersect-
ing, usually on a relatively large scale.
2.1 ASTM Standards:
D 660 Test Method for Evaluating Degree of Checking of
6. Use of Photographic Reference Standards
Exterior Paints
6.1 The photographic reference standards that are part of
2.2 Other Standards:
3 this test method and are provided in the Pictorial Standards of
Pictorial Standards of Coating Defects Handbook
Coating Defects Handbook are representative of the degree of
3. Terminology cracking of exterior paint films. Fig. 1 is for illustration
purposes only and should not be used for evaluation.
3.1 Definitions of Terms Specific to This Standard:
6.2 The use of the photographic reference standards illus-
3.1.1 cracking, n—that phenomenon manifested in paint
trated in Fig. 1 requires the following precautions:
films by a break extending through to the surface painted.
6.2.1 The accompanying photographic reference standards
Where this is difficult to determine, the break should be called
show line-type cracking only. Irregular and sigmoid-type
a crack only if the underlying surface is visible. The use of a
cracking may also be interpreted from these photographs.
magnification of 10 diameters is recommended in cases where
6.2.2 Care must be taken not to confuse various types of
it is difficult to differentiate between cracking and checking
failure that may be present on the same surface. This is
(see Test Method 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 Crackingfailureofpaintfilmscanoccurinuse.Thistest
6.2.3 It must be realized that the degree of failure will vary
methodprovidesameansofevaluatingthedegreeofthefailure
over any given area. Therefore, an average portion of the film
by comparing the pictorial standards.
should be used for comparison. On larger surfaces it is
5. Types of Cracking
recommended that ratings be made at several locations and the
mean and range reported.
5.1 Three types of cracking are recognized:
6.2.4 Paint films may collect excessive quantities of dirt,
5.1.1 Irregul
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