As a standard practice, when I get into camp, I immediately fill the platypus water bottle and lay it on a black stuff sack. With only an hour, the water is amazingly warm. This really saves fuel when cooking dinner and I get to wash up in warm water. The high altitude sun is definitely strong enough to create heat, it is just a matter of making an "oven". With the Bear Vault I used the aluminum foil on the back as a reflector and left the other side open to the sun. I think the air temperature at 12000 feet was just too cold. No, I did not turn it upside down. I have had cheese melt inside my Bearikade while I was carrying it inside my pack. So I think it may make a better oven. Other thought- just put the biscuits in a pot and put the pot inside a black stuff sack.