Acoustic Guitar Construction

I think I know those words too

I think each of us has an inventory of magic words, often used in an ascending order of profundity in sync with the seriousness of the provocation.

Well said Peter! lol

May be it's just me, but 35% humidity sounds very low. I guess it depends on where you live or where the guitar will be going.
I try to stay between 42% and 48%, and maybe a little higher if the guitar is going to an area like the US northeast.

Brent

I live in Connecrticut and I'm running central heat seven months of the year. I don't see a problem building in a generally-stable 35% humidity environment. Makes more intuitive sense to me than grinding away at the magical 40%. Magical for who? And why? I think the righteous arguments are begging the question, not answering it. I think building for the ambient environment makes more sense than quoting some 'rule'. I am also willing to be enlightened to see the error of my ways.

I think that in general terms, you better build on the drier side. Most guitar-crack-problems occur when humidity is low. Not when it is wet.
Herman

I don't believe there is a magic number for for humidity. Where I am, I'm using a humidifier to stay in the mid-40 range because June through September the humidity can often be 80-90%. Without my humidifier, I'm down to 20% or less in the winter. Staying in the midrange between the extremes has kept things pretty stable. I don't know how high the humidity swings are where you are. It doesn't take more than a 20% shift for a softwood like spruce to expand or contract noticeable. As I said in my earlier post, it really depends on your area.

Brent