Quote:
Originally Posted by drive-south
You want evaporative humidifiers for guitars. You also need to keep your house above 65 degrees or the humidity level will be zilch.
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There have been multiple threads on this---the actual air temp is irrelevant; we only care about the relative humidity level which will measure correctly regardless of the air temp. 50% RH is 50%, whether the air temp is 40F or 80F.
The confusion arises when air at a certain temp and RH is heated. The air has a set amount of water in it but can hold more if it is warmer, so air with *absolute* amount of water X at 40F might be 50% RH (50% of what it can hold), but when heated to 80F, that same amount of water would only be have 4% of the water it could potentially hold, because now that it's warmer it can hold more--thus 4% RH. You will have to pump water into the air with a humidifier, putting more absolute amount of water in that 80F air, to get it up to 50% of what it can now hold, or 50% RH.