Originally, as documented by Cennino Cennini (end of the 14th century), watercolour was intended as a procedure for shading sketches or drawings. Again Filippo Baldinucci (1681) defines watercolour as" a sort of colour that serves for colouring drawings; and one does this by putting two drops of ink in a lot of water, that which would fit in a nutshell." Beginning in the 18th Century, parallel to the definition of watercolour as an autonomous technique in England, the term indicates a painting executed with colours diluted in water with the addition of Arabic gum, as an adhesive, and of other substances (glycerin, honey, sugar), laid on a support, generally of paper. Different from gouache, watercolour does not foresee the use of white, given that light tones are used and the colour of the paper support is utilized. In restoration, watercolours are among those used for in-painting.