Earlier this year I bought some Damp-It humidifiers. These come with a useful little humidity gauge in the packet.
Here's the gauge that hangs out where my guitars are kept...
See all that pinkness? This is good. Basically the strip on the left has segments that change color with air moisture content. You can get an approximate reading (approximate enough to be useful for this purpose) by looking for the first pink segment and matching that to the figure (which is percentage) on it's
right left.
In even more simple terms, the more pink you see the higher the humidity, the more blue you see the drier it is. Currently it's all pink. That's not surprising given the weather we are having in Gauteng this spring.
This is good for acoustic guitars with solid tops, even more so for acoustic guitars that are all solid wood. It's just as good for any other solid wood instruments - violins, cellos, certain types of drums etc etc. (Damp-Its are actually made for orchestral instruments but work just fine with a guitar).
