Nope, only kosher salt, ...

nah I'm just kidding, any salt will work. Rock, table, or kosher. I've found that heat works really well too, although Ive never heated it to 90 c to find out. My thermostat won't go that high.

Come to think of it, that would be a good product for utah bio graydon, How about a thermostat that is capable of up to say 225f and as low as 135 f. Perfect for processing and methanol recovery.

Just a thought.