Has anyone ever tried varnishing the inside surfaces in the soundbox?

[Alan Carruth]

printer2 wrote:
" If thick enough it would help dampen the vibrations as would also happen on the exterior."

Finish adds mass, which increases the impedance and makes it harder to move the thing, but that's not 'damping'. The same goes for stiffness, which some finishes can add. Damping refers to the rate at which energy is dissipated (mostly into heat, but also into sound), which is the 'resistance' term in the impedance equation. Increasing any of those three things, mass, stiffness, or damping, raises the impedance, and makes it harder to get the thing moving, but only one of them is 'damping'.

Finishes can either add damping to a piece of wood, or reduce it. In his paper on this (CAS 'Journal', Vol. 3, #6, pp. 27-43, Nov. '98) Schleske reported on the effects of application of similar amounts of finish to cross grain spruce strips. In general, drying oils or finishes that contained them tended to raise damping, while resins had lower damping. Nitrocellulose and shellac actually reduced the effective damping of the strips: I suspect they added enough stiffness to raise the resonant pitches while not increasing the band width. The effect would probably be much smaller on a typical back wood.

Its hard sometimes to keep the terms straight, but it's worthwhile to make the effort, IMO. After all, I'm easily confused, and need all the help I can get....

[Riverwolf]

gotta admit that it can look a little unfinished and strange to see a beautiful and expensive guitar with bare wood showing through the sound hole. I also had a thread on this a few years back and someone posted pics of some guitars that had pictures showing in the open sound hole.