The author of Instructables under the nickname Team Bite tells how to make the right thing out of what we usually throw away - eggshells - chalk. But in a sense, this is “porridge from the ax”, because you also need flour.
The master takes the eggshell:
Separates the film from it, if any. It is most easily separated from large and wetted pieces of shell.
Boils the shell for disinfection:
Dries. He suggests using a microwave for this purpose, but this should not be done. With only one shell, it will work almost without load, which can disable it. It is better to dry without extra. heating, let it turn out longer. There is no photograph of this step.
The master grinds the shell with a pestle in a mortar:
Stirs with flour, if desired, you can add a little dye.
Slowly adds hot water, while mixing, and gets clay-like material.
Having made several holes in the plastic tube for the release of air, it pushes this “clay” there:
Leaves to dry completely:
And only making sure that the drying is really complete, extracts the finished result - chalk, which you can write on the chalkboard, mark something, etc.
The proposed experiment is closer to the physical than to the chemical, since no chemical reactions occur during its course. But this does not make him any less interesting.