This makes sense. Some come with adjustable levels of heat, you can find the setting that does the trick.
Originally Posted by Nicholas Lindan
I have one of the long black footwarmers. But I use it for my feet. It does give off a rubber smell, but not noxious. I think if you used the long rubber heating pad you would need a way to switch it on and off regularly because it would probably get too hot. I wouldn't submerge it but it sounds like your trays are on a counter. You might want to cover it with a shower curtain or something to keep the chemical spills from staining the ribbed surface.