How to Calibrate a Hygrometer

After being in the sealed bag for 8-12 hours, check the reading of the hygrometer. It is best to read it while still in the bag, since if your house air is dry the reading may go down quickly once you take the hygrometer out of the bag.

The relative humidity in the sealed bag with the salt/water mix should be 75 percent. My hygrometer read about 72 percent.