Originally Posted by MikeinCT
I think that if I could find a used variac it might be an easy way to make a simple heat element adjustable. There are also light dimmer circuits but I don't know if any of these could handle 20 amps!
There is no dimmer out there that will do what you need.
Well... there might be one... but it'll be prohibitively expensive.
same with the variac... it'll probably cost you several hundred dollars.