This is a non expert opinion
![Shocked :o](http://www.primitivearcher.com/smf/Smileys/default/shocked.gif)
Cheap and easy, is the Cheek test
![Wink ;)](http://www.primitivearcher.com/smf/Smileys/default/wink.gif)
Unless you are going to use your medium under,
other than ambient moisture content.
Touching your wood , leather ceramics etc.
to your cheek has worked for milennia.
If it feels cool or cold, it's more moist than 18 percent.
Zuma