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Message:: [QUOTE="2manybooks, post: 9761089, member: 8267"]I do know what shellac is. The surfaces that show the type of alligatoring/crazing I am referring to are generally much older than your 15 years of experience. Here are some typical recipes for shellac varnishes, from Varnishes and Their Components, by Robert Selby Morrell, published by Henry Frowde, 1923 :     - Shellac knotting varnish [for sealing wood] – orange shellac 112 lb, medium rosin 56 lb, methylated spirit 28 galls [denatured alcohol] - Cabinetmakers’ varnish – pale shellac 5 lb, mastic 7 oz, methylated spirit ¾ gall. - French polish – orange shellac 76 lb, manila resin 10 lb, pale French rosin 10 lb, methylated spirit 50 galls Looking at several other relevant texts in my library from the first quarter of the 20th century, it is clear that the recipes could be quite variable, and often included additional resins or gums. But shellac (from the lac bug) was the primary ingredient in varnishes used for interior woodwork until the development of synthetic resins in the mid century. The recommended processes include several steps for the preparation of the wood (filling and sealing), as well as careful instructions for the application of the final layer(s) of shellac varnish. At each step, the authors stress the importance of letting each application thoroughly dry (sometimes for several days) before adding another layer of filler/sealer/varnish. I suspect the problems of crazing and alligatoring may have resulted from workmen rushing the ideal process, and/or applying too many or too thick layers of varnish. Differential drying of the layers can cause the upper layer to "crawl" over time. Similar unfortunate effects can be seen in some oil paintings on canvas, where the artist disobeyed the rule of painting "fat over lean".[/QUOTE]

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