Board chalk, school chalk or write chalk is priority a material for describing rauen undergrounds, boards. It leaves small particles, which to the board sticking to remain loose and easily again to be wiped off be able. Board chalk is usually oblong with a square or circular cross section.
Chalk is made Austria and Scandinavia in Germany, first of all of calcium sulfate (gypsum), because most Kreidegebiete are protected there. In France one uses the mineral chalk for the Champagnerkreide in such a way specified - thus calcium carbonate. About 55 per cent of the chalk sold in Germany consists of gypsum.
Also multicolored chalk can be manufactured by additive of coloring materials. Since that chalk-deaf, which develops particularly when dry wiping the board off, is, for Allergiker disturbing, also dust free chalk is manufactured. The dust stands also in the suspicion to cause problems with the breath ways.
Teacher devaluing called Kreidefresser, although the idiom it has chalk eaten actually on the fairy tale "the wolf and the sieved young Geisslein" points, in its process the bad wolf for a flattering chalk eats sometimes, in order to let its voice sound gentler.
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