The hygrometer thread got me going on this.
Letting your shop environment change humidity levels is good!!!!!!!! Once
the instrument is assembled from all the parts they will continue to
change or try to change as well. There is no way around this unless you
keep it in your cigar humidor or in your continuously constant shop.
Once my wood is thoroughly dry, and seasoned, I let my parts cycle
through the seasons and changes in humidity and temp. I watch the parts
move a little. I don't clamp my plates down and restrict movement to
keep them flat. If I see something troubling like a warping back or side, I
might discard it or brace it differently.
I don't have a big volume of guitars, bass violins flying out of here so I do
have this luxury. This is a big part of my building process.
Understanding how much and which way wood moves is a big part of
mastering the craft. Which I haven't done yet.
Here's what's silly, to keep your shop at a constant humidity level. It is
expensive and unnecessary!!!!!!!!
.
But for all newbees and anyone selling or giving away a guitar, keep in
mind that any cross grain glue operation has to be controled and
performed in a low humidity state. Crank the duhumidifier for a couple of
days before bracing, and keep all parts out in the room to acclimate for a
a few days or a week. Keep both sides exposed to air and make sure the
air is dehumidified to a reasonable level. If you want to measure it, go
ahead, but it just needs to be dry. As to how dry, that totally depends on
where the instrument will live. Arizona is not worse than Boston as some
might think. A guitar braced at 45% RH going to Boston might reach 15 or
10% in the winter when the heater is cranking. And the back will want to
cave in.
Hedging for these extreme events is all about what makes you successful
and the instrument live a long life. Design proper bracing cross grain glue
only in a dry state.
Fingerboards should be kept at low humidity for longer since the dense
wood takes longer to acclimate.
