Quote Originally Posted by Roham
Hello everyone. First time posting:)

I am calibrating my hygrometer and I used 1/4 cup tap water with 1/2 cup salt stirred and placed in a ziplock next to the hygrometer over night. This morning it shows that I have 80% humidity in the bag. I had calibrated the hygrometer by wrapping it in a soaked distilled water cloth then after a few hours setting it to 95%(this was a week ago).


I am wondering what makes the salt/water mixture such an accurate way of judging the humidity? Exactly how accurate is that method, as opposed to wrapping it in a wet cloth? Thanks in advance.

Roham
According to other website information on the salt test, you're using to much water.

1 tsp. of salt in a milk cap size container along with a few drops of water. You do not want a salt water solution...only moist. That goes into a zip lock bag along with the hygrometer. Make sure that the hygrometer does not come into contact with the salt/cap. To make sure EXCESS air coming into the bag, it is reccomended to put the bag into another (perhaps larger) zip lock bag. Wait about 6 hrs and observer the hygrometer reading. The reading should be EXACTLY 75%. From that point you can follow the instructions for your hygrometer on how to calibrate the reading up/down to read 75%.