I have been looking for years for a decent tray heater. I bought one years ago from Nova. The guy told me it was the last one and it was 220v. I was lucky because I have 220 for my light sources in my darkroom but it was also about $200. ( yeah, back when I was more easily parted with my money ).
Well, I seem to be the Salt Lake City repository for old darkroom stuff and a batch came my way the other day with what I thought was a tray warmer. it was older than I am, that's pretty old, and gave it a try. it heated to 125f and did a great job of heating my developer for doing hot lith prints.
I started doing a web search and found that submersible heating pads only turned up junk for turtles, not what I was looking for. Then I looked closely at the pad I was given and found it was a mat. It's a heated floor mat for standing on cold cement floors.
Now this was hardly submersible, but boy, did it do a great job of heating my soup. Now... forewarning: In no way did this say it was submersible, but one claim said it was waterproof. So if somehow you end up electrocuting yourself, don't blame me. I do stupid things all the time.
So consider this link a suggestion: http://goo.gl/j8H3b
Anyone else thought of this or a better solution for our solution?