How to make a Solar Oven

Fold the top flaps closed on the outer box and set the inner box on top. Trace a line around the base of the inner box onto the top of the outer box

Remove the inner box and, carefully using the utility knife, cut along this line to form a hole in the top of the outer box

Decide how tall you want your oven (the inner box) to be. We recommend about 2.5 centimeters (cm) taller than your largest pot, and about 2.5 cm – 5.0 cm shorter than the outer box. (Note that you can change the height of the outer box in step 6, below.) This way there will be a space between the bottoms of the boxes once the cooker is assembled.

Carefully use the utility knife to slit the corners of the inner box down to the height you decided on

Cut the new, extended flaps completely off so that you are left with a box (without flaps) that is the height you want your oven to be. To do this, it is easiest to carefully use a straightedge (e.g., a hard ruler) and the utility knife or a pair of scissors.

*Set the inner box aside for now — you will not do anything more to it until step 9.

If you need to make the outer box shorter, do it now.

A. Remember, you want the outer box to be about 2.5 cm – 5 cm taller than the inner box.

B. If you need to change the height of the outer box, at each corner measure down to the new height you want the box to be and then make a mark there, along the box's edge. Then carefully use a straightedge and the utility knife or a pair of scissors to cut the box between the marked spots on the edges. You should end up cutting the box into two pieces as shown in Figure 5, below. Stack the pieces on top of each other (with one going inside of the other) and tape or glue them back together to make an intact outer box that is the correct height.

Glue aluminum foil to the inside of the outer box

Place some wads of crumpled newspaper into the outer box, so that when you set the inner box down inside the hole in the outer box, the cut edges of the inner box are even with the perimeter of the outer box. Also place wads of crumpled newspaper in the side spaces between the inner and outer box — this will help insulate the oven

Glue aluminum foil to the inside of the inner box.

With the inner box placed inside of the outer box, glue the top edge of the inner box to the perimeter of the outer box where they touch

Tip: You may need to use some tape to help hold the boxes together while the glue hardens.

Finally, make a shelf/heat sink inside the inner box. Cut a piece of cardboard the same size as the bottom of the inner box. Glue aluminum foil to one side. Paint the foil black using black tempera paint and allow it to dry

Once the paint has dried, put the shelf/heat sink in the oven so that it rests on the bottom of the inner box (black side up). The solar oven base is now finished

Take one of the large sheets of cardboard (that you will use for a lid) and set the solar oven base on top of it (centered). Trace the outline of the base onto the lid

Note: Be sure to orient the corrugations of the lid so that they go from left to right as you face the oven so that later the prop may be inserted into the corrugations

Carefully use the utility knife and straightedge (i.e., hard ruler) to cut through one (of the two) sides of the cardboard along the lines you drew. Then fold the cardboard down along the cut edges to make short flaps for the lid. Also cut the corner flaps so that the lid's flaps can all fold down neatly.

Glue the lid's corners to the lid's side flaps to make the lid, as shown in Figure 14, below. You may want to use binder clips to hold the corners together while they glue

When the lid is done gluing, make sure it fits on the solar oven base as expected

To make the reflector flap, draw a line on the lid, forming a rectangle the same size as the oven opening (inner box size). Cut around three sides and fold the resulting flap up to form the reflector

A. As you did in step 2, carefully use the utility knife to cut through one (of the two) cardboard layers where you want the flap to fold. Be sure to cut on the inside of the lid so that the cut makes the lid fold back the correct way (instead of folding inwards)

Glue aluminum foil to the inside of the flap you just cut out

Next, turn the lid upside-down and glue the oven cooking bag in place, covering the flap's opening

1. Use the turkey-size oven bag (47.5 cm × 58.5 cm, or 19" × 23-1/2") applied as is, i.e., without opening it up. This makes a double layer of plastic. The two layers tend to separate from each other to form an airspace as the oven cooks. Be sure to glue the bag closed on its open end to stop water vapor from entering the bag and condensing.

2. Alternatively, you could cut any size oven bag open to form a flat sheet large enough to cover the oven opening.

Make a lid prop by using a pair of pliers to bend a 30 cm piece of coat hanger wire.

Tip: You can carefully cut a piece of coat hanger wire to be this length by making a groove on it and then snapping it at the groove. Be careful handling the wire because the cut edges will be sharp!

Insert the lid prop into the lid's corrugations to hold the flap up. Your solar oven's lid is now complete!

Once the glue dries, your solar oven is complete and ready for cooking.