If you didn't think mold was a serious problem, guess again. Check out Jesse Greist's mandolin case. On the outside, it's not so bad, but taking one look at the felt interior shows an entirely different story. Jesse can't wipe the mold away from the felt because the felt will not dry.

Thus far, the mold has not affected his mandolin, which he still keeps in the case for transport. Costa Rica's tropical weather, however, does prove that it can upset your instruments.