For the completion of the work reproduced in bronze it has to be patinated or “coloured”, by consent with the artist on the basis of his specific request from a choice of samples, in order to raise the prestige of the work and emphasize the details of the modelling. This colouring or patina, is achieved not with paints, but with acids that we prepare according to our knowledge. These acids, expediting the natural process of oxidizing of the metal, behave in way that the colour seems natural for the sculpture, with the result that the patina is a part of the sculpture, and not a heavy blanket of paint.