Selected passages about the tempering of colours; on tempering with gum. If you wish to hasten your work, take the gum which flows from the cinus or the plum tree, and break it into very fine pieces, and put it into an earthen vessel, and pour a good deal of water upon it. Then put it in the sunlight or, in winter, on hot coals, until the gum melts and stir it diligent]y with a round stick of wood. Then strain it through a cloth and grind the colours with it. All colours and all mixtures of colours may be ground and applied with this gum, except minium and ceruse and carmine, which must be ground and laid with white of egg. Spanish green is not to he mixed with sap under varnish, but put on by itself with gum.