Fonctionnement - Solar popper

${#lang_bricoWikiWarnings_warning}$ The concentration of sunlight is very dazzling. It is therefore recommended to protect your eyes with sunglasses.
Put a little bit of water in the test tube containing the small black paper or aluminium foil roll (approx. 1/4).

Close the test tube with the stopper (plug). Place the test tube in the middle of the reflector.

While protecting your eyes, adjust the vertical and horizontal orientation of the parabola so that the focal point is exactly located on the test tube. (the shadow of the nail should be at its base).

Adjust the height of the test tube in its holder so that its base containing water is perfectly in the focal point.
The heat of the sun rays are absorbed by the black paper inside the test tube. The heat is kept inside the tube thanks to the greenhouse effect and increases.

The water is strongly heated and turns into steam. Its volume expands considerably (takes much more space).

Inside the tube, a very strong pressure is created, which finally expells the plug; BANG!
The parabolic reflector returns all the rays of the Sun at the same place, the focal point. The temperature can reach there over 200°C degrees!
Here is a short video of the solar popper.

Fixing the plug even stronger and with a little bit of patience, the explosion would have been even more spectacular !