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French Chalk is a term used by Max Doerner is his book "The Materials of the Artist" which describes a calcium carbonate used to make traditional gesso grounds.

"Chalk, calcium carbonate, dissolves in acids with effervescence (the carbonic acid escapes). Chalk is unaffected alkalis. When heated it remains white. Impure sorts discolor; for example, when they contain iron, they turn red. When strongly heated, chalk is converted into quicklime. Oil colors which contain chalk "set" quickly in the tubes. Chalk is not poisonous and has little covering power. The whiter it is, the greater its value; therefore French Chalk is the best. Precipitated chalk is a very fine material. Gray chalks are not useful in grounds; they develop ugly dark spots when touched by oil."

French chalk was a type of talc used by tailors for marking cloth, by cleaners for removing grease from cloth and as a dry lubricant in its powdered form.

French chalk has also historically been used for the repair of punctured inner tubes of pneumatic tires, such as are found on bicycles. A block of French chalk is typically included in proprietary puncture repair kits, which may include some means of generating a fine powder from the block, for example a small file or a roughened area on the metal case in which the repair kit may have been supplied. The French chalk prevents the repair from sticking to the tire.

Definition from Wiktionary, a free dictionary

English

Noun

French chalk (uncountable)

1. A type of steatite, used to mark cloth and as a lubricant in shoes, gloves etc.

Translations

• French: craie de tailleur f.