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I built this solar oven using these instructions. It's basically a big cardboard box with a smaller one inside it. The smaller one is lined with aluminium foil, and so is the larger one but you can't see that.. There's a lid with an ovenbag set into the top to make a window, and an aluminium foil reflector panel at the top. Underneath the pot sits an aluminium sheet painted black and raised slightly off the bottom of the oven with a few pebbles.
I put an oven thermometer inside before putting the lid on for the first time. Within minutes the temperature rose dramatically. Outside it was maybe 25 degrees, and in ten minutes it was 55 degrees in the oven.
Unfortunately it didn't get much higher than that. The heat outside did - it got to about 35 degrees that day, and the sun was burning down, but in my oven it didn't get any hotter than 60 degrees. Apparently you need 82 degrees to actually cook something. I don't know what the problem is. Does a commercial oven work better than this? I double checked all the instructions in case I missed something. I've read several other sites and double checked their instructions. I don't know what's wrong. Hmph.
If I ever work out the secret, then I'll make the oven beautiful - paper it with lovely paper or perhaps paint it or do some artwork on it. At the moement it's consigned to being ugly, unfunctional, and taking up far too much space. I shouldn't complain - so many of the things I've made recently have been an amazing success - to have had only one failure is really quite incredible.
Any ideas anyone?