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<p>[QUOTE=&quot;2manybooks, post: 9761522, member: 8267&quot;]Shellac is derived from the excretions of the lac insect. It is processed and refined into sheets which are broken up to create flake shellac. Shellac in this form must&nbsp; be dissolved in a solvent (typically some form of alcohol) to use as a varnish. Shellac is an ingredient, varnish is the product which includes a solvent and, historically, may include other ingredients as well. The terms have often been used interchangeably, although they have more specific technical definitions. The term lacquer is even more problematic - it can mean a solution of shellac, a synthetic resin, or, in Asia, urushi, which is lacquer based on the urushiol oil derived from Toxicodendron vernicifluum.</p><p><br /></p><p>&quot;French polish&quot; is one form of varnish based on shellac. It is distinguished more by the process of application than by the ingredients. There have been many other varnish formulations using shellac. All I have said is that there have been formulations of varnish, based on shellac, that have been used on interior woodwork that deteriorate in a characteristic way. If you read the link I provided from the Wisconsin Historical Society, it describes this as a known phenomenon. Just because French polish may not deteriorate in this way, it does not mean that other formulations of varnishes based on shellac do not. </p><p><br /></p><p>I really don&#039;t understand your objection to the observation that some forms of shellac varnish deteriorate. In fact, my hypothesis that the fault in these deteriorated finishes derives from poor application techniques would support the superiority of the French polish technique, which relies on multiple thin layers of varnish, dried and rubbed between applications.</p><p><br /></p><p>My initial comments may not have been as precise as they could have been. I was making a casual observation on the op&#039;s object. I did not expect to be writing a dissertation.</p><p><br /></p><p>Here are some additional references -</p><p><a href="https://cameo.mfa.org/wiki/Shellac" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://cameo.mfa.org/wiki/Shellac" rel="nofollow">https://cameo.mfa.org/wiki/Shellac</a></p><p><a href="https://cameo.mfa.org/wiki/French_polish" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://cameo.mfa.org/wiki/French_polish" rel="nofollow">https://cameo.mfa.org/wiki/French_polish</a></p><p><a href="https://cameo.mfa.org/wiki/Varnish" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://cameo.mfa.org/wiki/Varnish" rel="nofollow">https://cameo.mfa.org/wiki/Varnish</a>[/QUOTE]</p><p><br /></p>

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