Magazine article Acoustic Guitar

Gear Guru

Magazine article Acoustic Guitar

Gear Guru

Article excerpt


Q: I know wood selection, body shape, body size, and body thickness all contribute to an acoustic guitar's tone, but I find little mention of body finishes. I really enjoyed an old parlor guitar that had a thick woody percussive tone. I largely attribute the tone to the aged shellac finish on the guitar. My question is, how well do contemporary finishes age, and what types of tonal characteristics can be expected from different finish types and finish techniques as they "open up"?


A: Traditional finishes, such ^x\^ as varnishes and nitro^ ^ cellulose lacquer, take w x\^x: many years or even _ vxx decades to fully cure, while ^ catalyzed finishes, like urethane and polyester, can cure in a matter of days. Nitrocellulose, for example, starts out shiny, thick, and soft, and over decades becomes duller and harder, loses density, and develops myriad patterns of tiny cracks.

Vintage enthusiasts believe that the generally revered sound of older guitars is in good part attributable to the qualities that traditional finishes develop over time. Because the specific gravity of a finish is many times greater than that of spruce, the finish damps vibrations. No luthier would build a guitar without finish, however, because the damping property of finish is relied upon to filter unwanted frequencies. The trick is to select a finish that best compliments a guitar's design and voicing considerations, and to apply it in a way that damps undesirable frequencies, but doesn't damp desirable ones.

So, if some finishes take decades to achieve ideal damping properties, wouldn't it be better to apply one that already achieves optimal results for the type of guitar being built? And if an ideal finish could be engineered, why would we want it to change over time?

I try not to judge the relative merits of varnish, lacquer, urethane, polyester, and other finishes, for much the same reason that I cannot say Adirondack spruce is superior to European spruce, or that Brazilian rosewood is always a better choice than mahogany. …

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