With all the talk on the AGF about humidity, wanted to share this with everyone. I live in Guam where the outside humidity never drops below 75%. I keep all my instruments in an air conditioned room that maintains a temperature of 72 degrees and the drops the relative humidity down between 50-50%.
These are pictures of a guitar that I purchased on an international vacation trip in Asia. The top, back and sides are made of all solid mango wood. I don't know the temp and RH of which this guitar was built in, however, this is just to show that
50% RH isn't good for all woods. You can see the concave dip of the side right as the lower bout forms below the waist. This inward descending of the sides was
much worse as this picture was take after I took it out of the room and set it in my living room at 74% RH for 8 hours.
I've had it in 74% RH for the past 24 hours and it's slowly straightening out. Just glad I caught it before it formed a crack.