I just looked back into this thread, and I saw someone inquiring on how to calibrate your hygrometer.
There is a real simple test, called a salt test.
STEP 1:
Fill bottle cap with standard table salt; fill about 3/4 of the way up.
STEP 2:
Add tap water to the bottle cap to saturate the salt. If you see water floating on top of the salt, you’ve added too much water. Easy fix for this is to grab a paper towel, and soak up all of the excess water. You want more of a slurry consistency of water and salt. Again, if you see water actually floating on top of the salt, soak up the excess with a paper towel.
STEP 3:
Place both hygrometer and bottle cap (with salt/water mixture) in a jar, or a ziplock baggie. Wait 4 hours and come back for a reading check.
If your hygrometer is perfectly accurate, it will read 75%. Most hygrometers will be +/- 3 %. If your hygrometer is digital and has a calibration button, follow the directions that it came with to calibrate to 75%. Digital hygrometers have a calibration button you push, while analog hygrometers have a screw which allows you to adjust the needle accordingly.
STEP 4:
If your hygrometer is perfectly accurate, it will read 75%. Most hygrometers will be +/- 3 %. If your hygrometer is digital and has a calibration button, follow the directions that it came with to calibrate to 75%. Digital hygrometers have a calibration button you push, while analog hygrometers have a screw which allows you to adjust the needle accordingly.
If your hygrometer is not adjustable, you’ll just have to make a note and remember how far off it is.
Hope this helps.
HomieHogleg