I tried it out again today. About 8 ounces of water in the same steel cup. This time it was about 15 degrees warmer outside, less wind, and I made a lid for the cup with some heavy foil.

I broke one of the fuel tablets in half and lit it. The water was warming up but not close to hot enough when the first tablet started to be used up so I put a second one in.

It came close to boiling, I could see bubbles and steam when Wilma (my hiking buddy and favorite beagle girl) jumped up on the picnic table. You can imagine what happened.