Running, Sagging and Wrinkling Varnish

¶ Running, Sagging and Wrinkling. The causes for these troubles are substantially the same as for crawling. If the surface is vertical and considerable varnish is flowed on it is apt to run, sag and wrinkle as well as to crawl.

¶ The word curtaining is used to indicate the sagging effect of varnish when it sags in long ridges like the draping of curtains. This is apt to occur also near mouldings, carvings, etc., about which more varnish is likely to have been brushed than upon the open places. Varnish which is too new, which is unfinished or not aged enough will cause this festooning, but the trouble is more often faulty application of the varnish in the form of cold, wet, greasy surface or brushing on the coating in a film of uneven thickness. Slow-drying, elastic and durable varnishes containing more oil than the quick, hard-drying varnishes require more brushing and laying-off and are more likely to run, sag, wrinkle, etc., if not properly brushed to distribute the varnish in an even film.

¶ The wrinkling of varnish is caused by flowing on too much varnish. The outside surface absorbs oxygen and dries faster than the under side of the varnish coat, forming a skin. The under part of the varnish film gives up part of its volatile thinners by evaporation and thus loses part of its bulk. The outside skin taking on oxygen soon becomes too large for the mass of soft varnish under it and so it draws up into wrinkles or ridges.

Next Page: Silking or Enameling of Varnish.