Danny Moore wrote: > > Frank and list, I suggest that the refinishing process is largely a > matter of personal preference (within reason.) I've since deleted the > message, but I do recall someone mentioning the use of Defthane. I have > always stayed away from the use of Defthane or any other polyurethane > product on sound boards (or acoustic guitars, violins, etc.) because the > polyurethane creates virtually a "plastic" coating over the wood. > Sealing the wood in this manner would prevent it from "breathing." Danny, That's the whole point. You don't want a wood finish to “breath.” In reality, though, Defthane doesn't appear to offer any great improvement as a vapor barrier over other "natural" varnishes. It's just the resins are derived from a different source. And the material is physically tougher. Whether this is important in a soundboard finish is debatable. > I've never done any testing to determine if a polyurethane finish on the > board would alter the tone or resonance of the piano, perhaps Del or > others have. I would be interested in anyone else's thoughts on > polyurethane on a sound board. None that I could either hear or measure. > When it's my choice, I've always used nitrocellulose lacquer on boards > because I like the appearance produced by clear coating clean spruce. We also normally use nitrocellulose lacquer for the same reason. If varnish is requested we use one of several traditional "spar" varnishes. Varnish is susceptible to eventual breakdown when exposed to ultraviolet light. The "spar" in the name only indicates that the material has ultraviolet light blockers in it. The theory is that it will be more resistant to breakdown when exposed to sunlight. And, yes, there is UV even in reflected sunlight. ddf
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