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Old 05-26-2009, 10:35 PM
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Bruce Sexauer Bruce Sexauer is offline
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Location: Petaluma, CA, USA
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Catalyzed Polyester may or may not be a great finish, but it certainly is not varnish by any definition I am familiar with.

There are those who call Alcohol based finishes varnish, but it is what I call Shellac. They are likely Violin makers, not guitar makers.

Solvent based PolyUrethane seems like a varnish to me, but there is some technical difference having to do with Polymerization. I do not understand it.

Store bought varnishes come in two main categories, short-oil, and long-oil. Most Guitar appropriate varnishes are short oil, which essentially means they dry hard in hours to days. Long-oil dries hard in months or years, if it ever really does. Cabinet varnish is short oil, Yacht varnish is long oil, generally. The difference is often Tung-oil.

Rub-on oil finishes are generally detrimental to the wood in a musical instrument as they penetrate it and alter it's character. True-oil is one of these, along with Watco and similar Danish oils. Nice looking and feeling results can be obtained, but it is generally thought to be at some cost to quality of sound and longevity. Hearsay, but it makes sense to me.

Beside the "fact" that traditional oil varnish finishes are incomparably beautiful and some of us believe they promote noticeably superior sound, they have two other terrific advantages. One is that they can be applied by hand with complete success using just a decent brush and some abrasives. No special space or expensive equipment is called for. The other is that they are much more environmentally friendly than any of their competitors except French Polish.

French polish is shellac, and it is neither adequately durable, requiring regular maintenance and extraordinary care, nor is particularly easy to attain professional results. It does have in common with oil varnish a relatively thin coating, which many consider a performance advantage.
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