ASTM D660-93(2000)
(Test Method)Standard Test Method for Evaluating Degree of Checking of Exterior Paints
Standard Test Method for Evaluating Degree of Checking of Exterior Paints
SCOPE
1.1 The illustrated reference standards included in this test method are representative of degrees and types of checking of exterior paint films. These standards are primarily intended for comparative evaluation.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 660 – 93 (Reapproved 2000)
Standard Test Method for
Evaluating Degree of Checking of Exterior Paints
This standard is issued under the fixed designation D 660; 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 4.1.6 Shrinkage Type—Checking in which the breaks in the
surface of the film usually form individual short breaks with
1.1 The illustrated reference standards included in this test
shorter irregular breaks progressing at right angles.
method are representative of degrees and types of checking of
4.1.7 Short, Random Type—Checking in which breaks in
exterior paint films. These standards are primarily intended for
the surface of the film form short, irregular patterns. These
comparative evaluation.
breaks are usually individual and do not join.
2. Terminology
4.1.8 Sigmoid Type—Checking in which the breaks in the
surface of the film form oval patterns. These oval shapes rarely
2.1 Definitions of Terms Specific to This Standard:
complete their circle.
2.1.1 checking, n—that phenomenon manifested in paint
films by slight breaks in the film that do not penetrate through
5. Use of Illustrated Reference Standards
the last applied coating. Where precision is necessary in
5.1 The use of the reference standards shown in Fig. 1
evaluating a paint film, checking may be described as visible
requires the following precautions:
(as seen with the naked eye) or as microscopic (as observed
5.1.1 Since the type and degree of failure may vary over any
under a magnification up to ten diameters).
given area, a representative portion should be rated. It is
3. Significance and Use
recommended that ratings be made at several locations, noting
types and degree of failure.
3.1 Since checking is not easily recognizable, this test
5.1.2 Care must be taken to recognize that several types of
method is intended to provide, through definition and illustra-
checking may be present on the same surface.
tions, a means of evaluating the degree of this film failure.
5.1.3 Paint films may collect excessive quantities of dirt,
4. Types of Checking
which may mask the type and degree of failure. If necessary,
dirt should be removed by careful and gentle brushing with a
4.1 Many types of checking are recognized, of which some
moderately soft brush. Care must be taken not to damage the
are:
finish.
4.1.1 Irregular Pattern Type—Checking in which the
5.1.4 Fig. 2 illustrates microscopic checking under 10-
breaks develop in the surface of the film in no definite pattern.
diameter magnification.
4.1.2 Line and Short Parallel Type—Checking in which the
5.1.5 For convenience in recording the data obtained, the
breaks in the surface of the film are generally arranged in
records should be kept on forms agreed upon between the
parallel lines.
purchaser and the seller.
4.1.3 Switch Type—Checking in which the breaks in the
sur
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