How to Calibrate a Hygrometer - Put Hygrometer and Salt Mix in a Bag.
The cup with salt and water is placed in a bag (the hygromter should then be carefully placed in the bag, then the bag is sealed)
Lianne McLeod
Carefully place the cup containing the salt/water mix in a re-sealable plastic bag. Place the hygrometer in the bag, away from the cup of salt and water. Note: make sure none of the salt/water mix comes in direct contact with the hygrometer, or the hygrometer may be damaged. Completely seal the bag.