Items Needed:
1) Table Salt
2) Water Bottle Cap
3) Plastic Zip Lock or Air Tight Container

 

Step 1
Fill the water bottle cap with about a tablespoon of salt.

Step 2
Dampen the salt with water, should be 10-15 drops. Do not dissolve the salt.

Step 3
Place the salt cap and the hygrometer in your bag or container for 12 hours.

After 12 hours your hygrometer should read 75%.

If it does not and your hygrometer can be adjusted proceed with correcting it.
If your hygrometer does not allow for adjustment remember how much it is off by and make a mental note for the future.

ie. If your hygrometer reads 71% after completing the calibration (and can not be adjusted) 68% would be the equivalent of 72% within your humidor. Same can be said if it reads 79% after calibration 76% would be the equivalency of 72%.