Crazing of Varnish

¶ Crazing of Varnish. This defect is the appearance of fine interlacing cracks which seem to be in the under side of the varnish film, not on the outer surface. It is much the same effect as is noted on old china dishes. Automobile bodies are especially subject to crazing, even on the finest of finishes. The cause of this defect is often sudden changes of temperature. An automobile, for instance, may be stored over night in a garage with a temperature of 50 or 60 degrees; It is suddenly driven out into freezing or even zero temperatures. The metal surface contracts rapidly; if the varnish and whole body of finish does not contract in the same degree, crazing, or worse, may result. Then when the engine warms up there is heat on the inside of the surface and extreme cold on the outside. No wonder crazing is common with such extreme conditions. Crazing may result also from the use of excessively hard gums in the varnish and from the use of varnish which is not elastic enough for the job at hand, in other words, an unwise selection of varnish for the purpose.

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