SCENES

Nostalgia for Chalk


  • 1
  • By Imaginal Disc

Description

Sticks of processed ‘chalk’ are produced especially for use with blackboards in white and also in various colours. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk rock or limestone, while colored or pastel chalks are made from calcium sulfate in its dihydrate form, CaSO4·2H2O, derived from gypsum. Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO3 (calcite).

The first attested use of chalk on blackboard in the United States dates to September 21, 1801, in a lecture course in mathematics given by George Baron. James Pillans has been credited with the invention of coloured chalk (1814): he had a recipe with ground chalk, dyes and porridge.

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