Colour used to substitute gold leaf in order to obtain a similar effect to that of gilding. Mosaic gold is made of tin bisulphate crystals which, on the basis of the preparation process, have a yellow gold colour, more or less reddish. Cennino Cennini (end of the 14th century) - does not advise the use of mosaic gold in paintings- however, proposes a recipe for its fabrication which is essentially still followed today in industrial production.