When you wish to temper gorma, take strong quicklime and put it in a little jar. And when you have done that, take wine and water and egg white in equal quantities, and wet the lime with them. Then take the gorma and grind it on the marble slab with this composition. And when you have done so, you may work with the gorma, using that composition as a medium. And you sbould know that when the gorma is old, you may take water and put it in the gorma and leave it for a day; but take care not to have too great an excess of water, but add only enough water for the gorma to he affected by the moisture. And it will become as if it were fresh. If you wish, you may mix white with the gorma, and the colour will he tawny.