I also use Coleman stoves. Two, two burner units. Boiling a barrel uses a lot of heat.
i have a sheet metal tank, wit welded up ends. I think if it were insulated, it would take less heat.
Speaking of insulation, I had a brilliant idea of using a board to cover the tank to raise the temp. It worked quite well. However, do NOT use a board with ANY knots in it.
Why?
Well, uh,
When the knots get hot, they drip rosin into the tank. This interferes greatly with the even surface I just spent a whole day trying to get. Everything needs to be cleaned, de-greased, re filled, re heated, re boiled. Argh.
Tom