The absolute best thing you can do to maintain the wood and keep damage from occuring is to keep your instruments in a guitar specific hard case with a good in case humidifier. The case will cost you, but you can make your own humidifiers for about $2.00 each. Heres what you do:
Go to K-Mart or some such department store and find some plastic hinged lid travel soap boxes. Go to supermarket and buy some "O-Cello" sponge 4 packs. O-Cello brand are treated to resist bacteria & mold, so make sure to get that brand. Cut a 1"X2.5" rectangle hole in the lid of the soap box & cut the sponge for a snug fit. Saturate the sponge with Distilled water so that it does not drip. You can attach some velcro inside your case and on the back of the box if you want. I didnt. This Humidifier will keep a constant 40-50% humidity inside your case, which is what guitars really love! Do this & you wont be sorry!
Koy Carson
West Texas
The "PickKeeper" The ORIGINAL Guitar Accessory
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