I set up the solar oven at 10 am in the morning
Maybe too well: the pipe insulation I used as a gasket material melted, the double pane window cracked when it hit the nail sticking out of the melted foam insulation, the meat thermometer blew its bottom off and I nearly burned my fingers lifting the pot cover to check how the orzo was doing. This was all by eleven-thirty in the morning. At least the candy thermometer was surviving; it read close to 250 degrees F.
I stripped off the gasket stuff, pulled out the nails and used a couple at the bottom of the window to keep it from sliding. At twelve-twenty I had overcooked orzo, but a good cold rinse made it edible for a pasta salad.
I decided to try cooking some rice, but a lot of intermittent cloud started to move in and I gave up on it at two-thirty.
I lost less than $2 in materials (the thermometer was a 25 cent yard sale purchase and I used two lengths of pipe insulation) and gained a powerful solar appliance. The double-paned window cost $3 at the local ReStore and everything else was reused material: 2" foam insulation scrap, 1 1/2" insulation scrap, the green plastic corrugated box my greenhouse came in last year, and tarp material used for lumber bundles. I bought the dark granite ware pot at the hardware store for $10.
I don't know how long the tarp material will last. I may have to upgrade to something more substantial -- such as aluminum flashing painted with high-temperature paint. It certainly works fine as a heat absorber in my solar dehydrator.
The foam insulation sure keeps the heat in and carries the cooker through an occasional cloud. I'd like to get a true oven thermometer for it, especially if I decide to set up a reflector for it to try baking. I'll keep an eye out for one at yard sales.