Not being able to complete the solar oven until I located a suitably large piece of cardboard from which to make the lid, I decided to see what sort of temperatures I could get from it as it is. I have since procured a piece of cardboard, thanks to my uncle, so hopefully I can get to the lid this weekend.
I remembered that there was a piece of glass sitting unused around the house, so I cleaned it and took it outside. I set the oven base on the grass and put a cotton pad in it, and a cast iron skillet on the pad, and then an oven thermometer in the skillet. I put the glass on top. There was no angling the box so the sun entered it more directly, there was no reflector to direct more sunlight into the oven, and no black pan to help collect heat.
You know how your car heats up on a sunny day? A solar oven works on the same principle. The car is closed, and the sunlight enters through the windows. It strikes the surfaces inside the car and some of it is converted to infrared light. Most infrared light is heat. The darker the surface the light strikes, the greater the amount of light that is converted to heat. Once the light is converted to infrared, it cannot pass back through the windows. Hence, black vinyl seats = burned tush.
In a solar oven, you want the heat concentrated where the food is. This is why the inside of the box is reflective. You want the light to keep bouncing around until it hits the dark items, which are the tray and the pots. The oven will heat up, as well.
Now, I had meant to get the oven outside earlier in the day, like about 8:30 or 9:00, but I forgot about it until 11:30. In spite of that, the temperature of the oven at 2:00 pm was around 210*-215*!
Not bad at all for an unfinished solar oven!! Yeah!!!
It is good to have the oven reach at least 250* for cooking, to provide the safest temperature rise and not allow too much bacterial growth. This is about the temperature a crock pot operates at.
Some solar ovens are all black in the interior. They work on the same principle, just preferring to have all surfaces of the oven involved in converting light to heat. I don’t know if either is superior, and there seems to be disagreement on that point. Ah, well, as long as the thing cooks!