Scito etiam

Know, also, that any colour newly tempered will not shine until it has been fattened on the fatness of the glair for from two to four days , since by nature it is lean and matte. Now when you first put the glair onto the colour, stir the colour all up, and mix it with the liquid, so that the whole mixture may thus fatten equally. Still, when you find that the colour has become thick and lustrous, and that it threads like glue, and hardly flows from the pen, then it is too fat, and you must modify it with water so that it may not be as I have just described. It is desirable to have the whole mixture covered with tempera; but let part of the colour settle to the bottom of the dish of that colour or colour-vessel, and stir the other part as usual with the regular stick. I have described it for this reason, that you may always be able to temper these things at any moment according to your wish, either so that they will shine, or not shine at all; or wherever they are not shiny enough, or wherever they are too much so; by means of water and glair.