Tested the performance of stock beer can versus black painted cans versus wire-brushed can. Tested the following Foster’s beer can pots (left to right): stock can, stock can with bottom painted black, stock can with lower 1/3 painted black, stock can painted entirely black, and wire-brushed can.
All boil tests were conducted with 70* F water, air and alcohol, at sea-level air pressure, using 2 cups of water and 14 grams of KleanStrip SLX alcohol. Stove is my own design, which I have dubbed the “Ramjet.” Windscreen is .003" stainless steel cone. Did four boils with each can and averaged the times.
5:25 (325 sec) Stock can
5:19 (319 sec) Bottom black paint
5:18 (318 sec) 1/3 black paint
5:15 (315 sec) All black paint
4:56 (296 sec) Brushed can
Conclusion: black paint reduces boil time compared to stock can, but brushed can reduces boil time the most. Stock can takes 10% longer to boil than brushed can. Since the stove burns at the same rate regardless of the can, the 10% difference in boil times between the stock can and the brushed should result in similar fuel savings. Will test that hypothesis next.