Calibration of your Hygrolid hygrometer is typically quick and easy.
To calibrate, simply use a small standard head screwdriver to turn the screw on the backside of the hygrometer and set the pointer on the face of Hygrolid to a known Relative Humidity (RH). Use slight inward pressure with the screwdriver when calibrating. If the face of the hygrometer spins when attempting to calibrate, apply light pressure to the face of the hygrometer and simultaneously press the screwdriver inward more firmly and turn to release the pointer.
There are a few of simple methods to determine the RH for calibration.
1. Place Hygrolid next to another hygrometer which is properly calibrated and wait a while (Waiting times will vary. It may take nywhere from 15 minutes to several hours or overnight depending on conditions). Set the Hygrolid to match the RH% of the other hygrometer. Digital hygrometers are fine for this method. Recheck the calibration a couple times if you have any doubts.
2. SALT and WATER. RH 75%. Place a tablespoon of salt and a teaspoon of water into a small widemouth canning jar. The salt should be wet but not dissolved or watery. Use the ring that came with the jar, lightly screw the Hygrolid onto the jar and wait for the hygrometer to adjust (Waiting times will vary. It may take anywhere from 15 minutes to several hours or overnight depending on conditions). Set the pointer to 75%. Recheck to see that your calibration is accurate.