lament wrote:It is my understanding that many problems with wood are caused by changing moisture content due to changes in atmospheric humidity.
Wouldn't sealing a (properly cured, of course) piece of wood with a finish impervious to moisture eliminate all humidity-related problems? What am I missing? Does wood need to breathe?
That finish doesn't exist. All finishes "breathe". Thin finishes pant. (And thick finishes damp.) There's room to argue that a bit of finish on the inside of a guitar might protect against very brief humidity variation, but after a few days at most, the wood will start to move.
A hermetically sealed case could offer protection, or it could make things worse if the temperature varied.