How to Build a Solar Box Cooker

A Solar Box Cooker is a solar oven made of cardboard, aluminum foil and a sheet of glass. These ovens can reach temperatures between 225 and 400 degrees Fahrenheit and are great for cooking food on a sunny day. To build a cooker (diagram 1), you will need: 2 cardboard boxes (one larger, one smaller), fiberglass insulation, silicone, glue, glass, aluminum foil (or aluminum tape), black paint, a piece of cardboard to make a lid, and a stick or string to hold up the reflector.

Here are the basic steps:

1. Find two boxes. One box should be 4 to 8 inches larger than the other in each dimension. Place insulation in the bottom of the larger box. Now, place the smaller box inside the larger box. Fill the gap space between the two boxes with insulation. Now tape or glue the two boxes together at the top as seen in diagram 2.

2. After you have the two boxes assembled, you should have what looks like a really thick box. Now paint the inside of this really thick box black.

3. Now make a cardboard lid to fit over your really thick box. The lid will help trap heat inside the box. It should look something like diagram 3. Make the lid a little larger than your really thick box, so that it will slide over top.

You can make a good lid by taking a large piece of cardboard and making it into a shallow box about 4 inches deep. Use glue to hold your shallow box together. Now cut a hole in your shallow box to form a cardboard flap for the reflector (see diagram 3). The cut for the reflector should have three sides, leaving one side for the reflector to be attached.

4. Glue aluminum foil to the cardboard flap (reflector). You can also use aluminum tape.

5. Now silicone a piece of glass in the hole where the reflector was cut out (see diagram 1 and 3).

6. Attach a string or stick to the reflector to adjust its angle to the sun. You want as much light as possible to enter the big black box.

7. Put food in the box. Point the box south and wait several hours. Make sure its sunny.

And that is all there is to it.

Make sure you wait for a sunny day, or your food won't cook. It also helps to put a thermometer in the box to check the temperature. In Arizona, I was able to get about 350 degrees out of my box. If you are going to leave your box all day, point it south, because the sun moves in the sky, but is always tipped south in the summer (in the northern hemisphere).