Calibrating Your Hygrometer
Tips on Dialing in Your Hygrometer
Hygrometer Calibration Paper Towel Test:
If you are looking for alternate option, this calibration procedure is a bit more technical. For you chemistry buffs, when water (H2O) and salt (NaCl) are in a saturated solution at equilibrium, the result is 75% relative humidity. This provides for an excellent point of reference to calibrate a hygrometer.
To get started, fill a bottle cap (from a water or soda bottle) with regular table salt. Next, place a few drops of water on to the salt to create a dampened mixture. Make sure you do not add too much water where the salt dissolves or turns into a liquid solution. Next, place the cap and your hygrometer inside a zip lock bag or a plastic container and seal it. Wait 5-6 hours and check the value on your hygrometer. If the reading is 75%, your hygrometer is accurate and calibration is not necessary. If the reading is not 75% and your hygrometer is adjustable, adjust the calibration screw on its backside to 75%. Room conditions will quickly influence the hygrometer humidity reading so the adjustment must be done immediately upon removing the hygrometer from the bag or container.
For those who do not have an adjustable hygrometer, you will need to remember to add or subtract the difference between the test reading and 75% to determine the actual humidity level within your cigar humidor. For example, if your hygrometer test reading was 85%, then subtract 10% from the value when the hygrometer is in your humidor.
Please know that digital hygrometers are pre-calibrated and set from the factory and are generally far more accurate than analog hygrometers. If you have a good amount of expensive cigars, and keeping tight tabs on your humidity levels is important, its suggested that you pick up a digital hygrometer.