This is the simplest solar cooker I've been able to design:
Instructions[edit | edit source]
Use a cardboard sheet 60 cm x 80 cm or larger.
Draw lines to divide in 2x3 parts, and cut "A" lines only.
The dotted lines are all for concave folding, so you can make a careful "half-cut" and then it will be easier to fold.
Make two holes, so that the string will go through the holes once the red parts are below the yellow part. The string is knotted like your shoes'. Not a permanent knot because you want to be able to take the kitchen to other places.
Glue foil paper to the part of the cardboard closer to you. Maybe the inner side of some fried chips bags. If there's no glue you may staple it.
The bottle with the bottom cut off (and discarded, unless you find a use for it) helps in getting more greenhouse effect. You can place it on a circle made of sand so that it's more air-tight, so almost no heat should come out there.
Inside the "greenhouse" you could place a glass jar, with its lid. Both the jar and the lid can be painted black with some kind of paint that doesn't produce toxic vapour when heated. Coal with rice water or something.
Careful, it's hot! I don't think temperature goes above 100ºC. Use folded cloth or gloves to grab the hot jar.
Public domain, so copy, modify and use at will. Experiment and tell us.