Grind azure on the stone, and then strain it through a fine cloth, so that it may be cleaner. When it is clean and dry, add to it some fresh, strong egg white. Then take some of the yolk of a raw egg, and mix it with water, or with a little wine, and put a very small amount of this into the colour, and it will make it flow better from the pen. That same device is useful for all colours, for the same reason. And if it is too dark, you may wash it two or three times, or as often as you like, briskly, with water, and it will be improved.