mjbphotos
Moderator
45%-55% for acoustic guitars is best. Electrics are not as fussy, but stable humidity is best for all. Don't use a 'cool mist' humidifier unless you put distilled water in it - otherwise you'll get a white powder film on everything. Get a digital hygrometer or 2 (you can find them on fleabay for $20), the cheap one sar enot too accurate, but you just need to know that you're in the range.