After reading many posts on this board suggesting that maintaining ~80% humidity in a cave is harder than it looks, I began to suspect that my little humidity meter (a freebie in years past from orchid growing supplies) was substantially off. It has been telling me that I'm sitting pretty (in my cooler with 2 pie pans of water at 55F) at about 75-80% humidity.
I bought a new digital humidity gauge and confirmed its accuracy using the salt +DI water slurry method, and then threw it into the cave, to find that I'm actually at around 50% humidity. So, since the salt + DI slurry brings the air to 75% humidity (the basis of the accuracy test), I figured I'd try that in the cooler. I added a small bowl of salt slurry, and today the humidity is up to 80%, according to the new digital gauge.
Has anyone else tried this? I still disbelieve for some reason....