— Begin quote from “jwpropane”
What is the correct humidity supposed to be anyway?
— End quote
40% to 50% is the normally quoted range. 50% seems a bit high to me, and my target on my non-calibrated h-meter, I shoot for 36 and above.
Here’s a bunch of anecdotal observations that are worth the price you pay for them… I have yet to get out my humidifier during the summer, and it is not abnormal to see 35% when the AC was running a fair amount. In the winter, once we get Northern air masses in here to stay, I run the humidifier all the time, unless we get the gulf air mass here and it gets up to around 45% (on my non-calibrated h-meter). When I have trouble keeping the house at 35%, I take the instruments off the walls, and they go into the cases, often with case humidification. Below 35% is where I start getting static, dry skin, nose bleeds, etc. It may seem odd to say I don’t worry about 35% in summer but I start worrying around 35% in winter. There is a basis to that other than my observations on how the guitars are reacting: Dry cool air is different than dry warm air . The air’s capacity to hold water doubles with about every 10 degrees F (hat tip to my meteorology professor). There is more water in the 35% air that is 76 degrees (my summer indoor temp) than there is in 35% air at 68 degrees (winter). I have found that moisture in the closed case does seem to migrate well. I have put the h-meter in the headstock area with humidification in the body or even the accessory case. After leaving it shut overnight, the headstock area was nicely humidified as well. I know people that never humidify, they have guitars out all winter in KY, they probably have air that stays in the 20 something % range for weeks on end, and they haven’t had any cracks. I know people that have left their instrument in car (in winter) for an hour or two and ended up with multiple monster cracks right then and there. I think rapid changes greatly increase the likelihood of cracks, but that’s just a hunch based on what I have seen. Instruments (particularly rosewood) seem to sound much better when not overly humidified.
That’s about all I can think of. Some of it may be right, but I am certainly no expert.