Fresco (from the Italian "a fresco" which means "in the fresh") is a particular mural painting technique that is applied to a fresh plaster called "intonaco", before it is dry. Painting on a plaster that has not yet dried allows the pigments to penetrate the mass, and therefore the colours to last longer than a simple surface painting on a substrate.

A complex chemical process, called carbonation, comes into play from the first application of the plaster on the support intended to receive the fresco and will harden until it becomes again the exact same limestone as it was originally! It is for this reason that we can say of the fresco painter that he paints in stone.

He has very little time to complete his work (usually just under two hours). That is why the large frescos are made slice by slice. It is not to say that fresco is an art that requires a great mastery of both gesture and material.

Pierre Testud, restorer and frescoist, who trained at the Venice School of Frescoes for several years, presents here the reproduction of part of the frescoes of the Chapel of Our Lady of the Fountains, at La Brigue, Alpes-Maritimes, a chapel famous for the complexity and profusion of its frescos, dating from the 15th century and attributed to Giovanni Canavesio and Giovanni Baleison.