I used to, as Judy suggests, use those aluminum coils to heat up my Agfa
color chems in the mid-60's. It took a bit of tilt, tilt swirl, swirl
and an even temperature was spread throughout the trays (20"x24") …
however, they DIS-appeared after a few days use. Hmmm!
Today, I dash down to the Goodwill/Salvation Army or pop into a large
store when a sale is on to purchase teflon covered adjustable temp
frying pans and use a stainless steel beaker. [ If any serious
photographer does not have a stainless steel utensil one should be
purchased (check on type when buying as some have more 'oil' in them and
actually can corrode in photo chem) ]
The heated chemistry can be poured into your tray prior to development
and perhaps a floating tray of stainless in a water bath would help or
even do the trick in the 1st place.
JF