Method, devices and media for writing and drawing, particularly for children and corresponding games, using chromogenous reactions sensitive to pH

摘要

The invention concerns a method of writing and drawing intended for children, and in some cases for adults. The writing medium consists of a paper impregnated with a substance whose colouring varies according to the pH, and the writing device carries an element modifying the pH locally, which leaves a mark. Used to obtain unusually coloured effects. IMAGE