How do I calibrate my analog hygrometer?

The most gemon way to calibrate your analog hygrometer is using the salt method. To start, place a teaspoon of salt in a small plastic container such as a bottle cap. Go ahead and dampen it with a few drops of water but do not let the salt dissolve, you just want to moist the salt. Once the salt is moist go ahead and place it with your hygrometer inside a plastic clear container and close tightly. Leave it sitting for at least 6 to 8 hours and inspect the reading on the hygrometer. The hygrometer should should read 75% humidity. If the hygrometer reads any other reading that is how much your hygrometer is off. If your analog hygrometer is off the 75% humidity mark you will need to adjust it to the 75% mark. The way you do this is by turning the screw on the back of your hygrometer by using a small screwdriver. Long ashes my friends! Your hygrometer is now ready to use!