Alligatoring of Varnish

¶ Alligatoring of Varnish. This trouble is noted most often on doors and window frames, sills, casings, etc., which have been grained or painted. The cause is the use of too much oil in the painted or grained under coats. The paint is more elastic than the varnish, so the varnish film breaks to let the paint expand more when heated by the sun or otherwise. Paste fillers mixed with too much oil and used on woods which do not absorb much oil, or when not allowed to dry hard before varnishing will sometimes cause alligatoring. The alligatoring of varnish is caused by the use of quick-drying, short-oil, hard varnishes over long-oil elastic varnishes. Alligatoring, of course, is that condition which causes the varnish to break up into cracks which look like an alligator's back.

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