I used kosher salt, salt. Do you want a pic? I used exact measurements with measuring utensils. I have Morton but there is another ingredient in it for caking.
Do I really need to calibrate a hygrometer? The salt test isn't working, it doesn't look like slush. I put a table spoon of salt and a teaspoon of water it doesn't look like slush, I added a little bit more water, should it be fine for calibration?