Until today, the coldest day on which I had cooked food using a solar oven was 50 degrees Fahrenheit. The temperature today was in the upper 30s and the sky was completely clear, so I decided to try my luck. I used my best insulated box oven and placed inside it an oven thermometer and a black pan containing three eggs.
At 1 pm I checked the thermometer to see that it had reached 215 degrees, hot enough to cook just about anything with enough time. I became engrossed in other things until 3 pm at which time I checked the oven again. By this time, the sun had sank low enough in the sky that the box was in the shade and the temperature had fallen to 100 degrees. I took it inside and found the the eggs were completely “hard-boiled” and ready to make egg salad. Of course, there was actually no boiling involved because with a solar oven there is no advantage to including water with the eggs.