In some parts of the world, the power supply is miserable, but the weather is usually good. There, many people have made a virtue out of necessity: they cook with solar energy. You can too!
- a postal packet (size S *)
- a postal parcel (size L *)
* Attention: The sizes refer to packages of Deutsche Post. If they look different in Austria or Switzerland, for example, the size of the glazing film may change. This is adapted to the lid of the smaller box, otherwise everything stays the same.
- two to three old newspapers
- black poster paint and brush
- several meters of fabric tape (about 4 cm wide)
- about 60 cm insulating tape
- two pieces of glazing foil (about 1 mm thick, 17 x 24.5 cm in size) from the hardware store
- aluminum foil
- four pins
- Scissors or cutter
- Pencil and ruler
Postal packages can be purchased as a kit in all post offices. This is what you first put together according to instructions. To make them hold better, you should glue all parts together – except for the lid of course. The fewer holes and gaps your oven has, the better it can be heated!
Seal with the fabric tape all edges on the sides and bottoms of the boxes. This also serves for better insulation. Then you paint the smaller box from the inside full of black paint.
As the paint dries, you devote yourself to the bigger box again. Its lid will later serve as a reflector, which also directs sun rays into the oven and thus provides even more heat. First coat the inside of the lid evenly with glue.
Then carefully and smoothly lay a layer of aluminum foil on it. It always has a dull and a more reflective side. The latter should be visible! So that the film does not tear at the edges, you stick the edges of the lid also with fabric tape.
From the lid of the smaller box you cut out a rectangle – so big that at the edge of each two centimeters of cardboard remain. Pick up the cut-out rectangle, you’ll need it later.
Now you stick one of the pieces of glazing foil against the cardboard edge of the lid from both sides. This creates a heat-storing double glazing. Take care not to smear the windows with glue!
Three sides of the lid you provide from the inside with insulating tape – as in the picture. Then your oven closes even denser, and less hot air escapes.
Is still missing the isolation: Rip the old newspapers and crumples their shreds together. Put a layer of it in the bottom of the big box. Then you put the little one on it. Also fill in all the gaps between the two boxes with your paper.
Finally, you cut a strip off the leftover cardboard rectangle from the lid of the small box. You fasten it with a pin on the lid and on a narrow side of the big box. By moving the needles, you can set the angle at which the aluminum foil faces the oven window.
Now it can start! Find a sunny spot where you set up the stove. Remember: the sun is constantly moving in the sky. Therefore, it is smart to also regularly reorient your solar cooker. Sets the reflector lid so that it also directs sun rays through the viewing window. Make sure that the lid of the smaller box is properly closed. If in doubt, secure the locking tabs with one pin each.
Of course, a cardboard box does not get as hot as the home bakery. Nevertheless: 100 degrees can easily reach. This is enough to cook sausages or to warm up the lunch sometimes. Whatever you want to put in the oven – it should not be placed directly on the bottom of the carton, but in such a way that heat comes from below – for example, by building a kind of rust from a few forks and placing the sausage on it. Only stay with us, to wish you a cloudless sky!