Humidity is important. When I build a guitar in my shop, I try to control the humidity. The wood must by dry. I have three ways to change humidity. First is a dehumidifier. It gets used mostly in the summer, but rarely even then. I have a cool mist humidifier. I also have a heater. The heat lowers the humidity in the shop quite a bit.
But before you control it, you have to measure it. I have two moisture meters to measure the humidity in each piece of wood that I use. Both give similar readings but I have two to make sure that every piece of wood that I use is as dry as it can be before it goes into a guitar.
Humidity in the air is important when building instruments. I control it with a dehumidifier, or a humidifier when the relative humidity in the shop goes too far up or down. How can I tell?
I have a favorite hygrometer. Here are three. Notice that they all report the temperature as 68 degrees Fahrenheit. Relative humidity is another issue though. One reports 45%, another reports 33%, and another 38%. Yes. Different hygrometers give different readings. The numbers seem exact until you realize the validity is in doubt due to individuality of the devices.
Here’s some photos.
Which is correct? Boveda makes a little kit to test. There is a sealable bag with salt crystals soaked to a specific relative humidity. In 24 hours I can see what this hygrometer reads…