ASTM D661-93 pdf free.Standard Test Method for Evaluating Degree of Cracking of Exterior Paints.
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.
The use of the photographic reference standards illustrated in Fig. 1 requires the following precautions:
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.
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.In examining wood panels for cracking failure， thepossibility of wood failure should be recognized.This takes theform of a cracking or splitting of the wood itself with aresultant rupture of the paint film. Also，some panels willdevelop “resin spewing?’which will cause early failure bycracking.These points should be taken into consideration inany evaluations.ASTM D661 pdf download.