Stereochromy

A style of painting on plastered walls or stone, in which the colors are rendered permanent by sprinklings of water, in which is mixed a proportion of soluble glass (a silicate of soda).

a process of mural painting in which the pigment is fixed by a series of reactions between the lime, fluosilicic acid, and water glass.; "The ground for stereochromy has been modified several times since the first introduction of this method of water-glass painting."