Steve Pearson wrote: > > Sorry...more on varnish. Many varnishes, known as "spirit varnish" are > various gums dissolved in alcohol. Oil varnishes were essentially the > same with the addition of oil, usually linseed. Both will react like shellac > when alcohol is applied. Modern varnishes from the hardware store > are a far cry from the varnish of a few decades ago. > Steve Steve, The big difference between varnish and shellac is that a varnish (any kind of varnish) is a "reactive" finish as opposed to an "evaporative" finish. What this means is that a varnish finish has a critical ingredient (usually linseed or tung oil or gum) which goes through a chemical change to form a surface film. This change causes the molecules to link and form larger molecules. Because of this chemical change, a reactive finish can not be redissolved. In an "evaporative" finish, such as shellac or nitrocellulose lacquer, the surface forming action is controlled by a solvent which simply evaporates and leaves the dissolved resin on the surface. An evaporative finish can be redissolved by its own solvent at any time. Sorry if this sounds too much like a lecture. Frank Weston
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