This instructable is about a solar oven I made out of an old picture frame, two cardboard boxes, some duct tape, aluminum foil, white glue and crumpled newspaper. You will need to find a picture frame. I used regular glass but tempered glass would be better as it gets very hot and could shatter if you spilled cold water on it. I think I used about a 12 x 14 frame, not sure as it was a few years ago. What ever size glass you find will decide the size of the inner box and the outter box should be 2-3 inches larger. You need to cut a hole in the larger box to fit the inside box then crumple up some newspaper and pack between them.
Next thing after the box is in the hole and newspaper is packed between them is to tape it up.
Next I lined the inside with aluminum foil using white glue. After I tested it I extended the foil out of the box and over the top. I also reversed the door so the tape was on the outside. Sorry I have no photos of the modification. I used two layers of Duct Tape for a hinge on the back of the picture frame.
Next are the reflectors. I made them out of cardboard but corrigated plastic political signs would work perfectly (After the election and with permission) I cut out the cardboard and applied white glue and flipped it over on to a sheet of foil shinny side down. Trim the foil after it dries and add Duct Tape around the edges. The best angle is around 60 degrees off the glass. I was just learning when I made this so my angle was off so I corrected that later, again no pics.
Time to start testing. I tryed different methods of aiming the oven by blocking with rocks, bricks or leaning it against something. Found it didn't do a very good job of baking rolls as they came out hard as a rock but I cooked a chicken breast in it in 2 1/2 hours. I had to tweek the reflectors to get the right angle for the sun to focus on the pan. I poked some holes and used a shoe lace to adjust the light beam.
I poked a hole through the back and inserted a probe type thermometer. I had it up to 280 degrees when we was in Arizona on a nice February. We used this oven for a couple weeks then I built "The Solar Baby" a pivoting, gimbled solar oven, I made 2 instructables on Solar Baby 1 and 2, made mostly with recycled parts and reach 350F. This project is what got me hooked on solar cooking. We have been on the road in our motorhome 3 years and only use our propane oven on cloudy days.