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