As an object the commedia dell'arte mask is a false countenance made of leather. It is commonly thought that it was black, ab origine , but this is not the case: it was of natural tan colour when new, only becoming blackened with use and age. In the olden days, performing in the open air or by candle-light, it might take two or three generations of wear for a mask to blacken totally. Furthermore, the mask-makers of the time did not have the means to introduce different colours. The most important disciples of Decroux are Eugenio Barba of Odin Teatr and Jerzy Grotowski who developed the idea of the corps plastique. The costume is part of the mask in fact, the only non-masked part of the actor is his hands. But on stage, rather than on canvas, one learns what the author call the ‘principle’ of the masks.