Article: Too much of a good thing!
If you can't stand the heat (and humidity) get out of the kitchen.
I'm always lecturing customers on the dangers of drying out
instruments. Each winter I see several cases of severely dry guitars- concave
faces you could drink soup out of, sharp fret ends, loose braces, and split
center seams. This year I fixed an 8-inch-long side crack on an obviously
parched guitar (a new Martin). Warranty? Forget it!
But the opposite situation is just as dangerous, in different ways. This guitar is owned by a young lady who does Christian missionary work in Costa Rica. She lives in the jungle in a house where the windows are just holes in the wall. A probably well-meaning but clueless salesman told her that a Martin D-15 would be the best choice to take with her to this environment.
When you are trying to take apart a guitar, you use heat and moisture. Guess what this instrument had plenty of? The neck had pitched forward, the sides had parted company with the back, and every back brace was loose. Interestingly, no top braces were loose, nor was the bridge.
The 15 series Martins are built with a mortise-and-tenon neck joint, reinforced with a single bolt. The bolt alone is not strong enough to hold the neck, and is really there to speed assembly- they don't have to clamp the glue joint. I consulted with the Martin repair department about the repair, because I thought I might be able to steam the joint and squish it tight with the bolt without taking the neck off. Unfortunately, without the strength of the glue the bolt anchor in the heel will sometimes pull out, so no quick-and-dirty job here. I had to remove the neck so I could tell if the bolt assembly was sound. (By the way, there's no reason to assume a traditional dovetail joint would have fared any better.)
You can see that the side has slipped, leaving a little "shelf" of back protruding. It looked like this on either side of the endblock.
Here's a closeup from a slightly different angle. See the stringly glue? It got like gum on the bottom of your shoe. I should have put a ruler in this photo, but you can see that the side has moved about the same amount as the thickness of the back.
Here's the gap at the heel. It was solid; no way to mash it back flush, because now the glue has cooled and hardened again. This resulted in unplayable action because any movement here results in five times as much movement at the nut!
I pulled the neck, removed the old glue, and reglued it; I
glued all the loose back braces, and I realigned and glued the back edges.
Unfortunately for the young lady, this sort of mistreatment (though unintentional)
is not covered by warranty.
The moral? Be informed! Seek out sites like this one, and guitar forums. The store sales guy may not be as knowledgeable as he seems.