The second, and perhaps still better method of preparing canvas, is by the use of a tempera ground. For this method a raw or quite unprepared canvas is best. Take powder (i.e. tempera) flake white and mix it with a well-beaten egg, using both the white and yolk. Some artists use only the white of egg,but this does not form such a strong cement, and the slight tint of colour from the yolk is no real drawback. A stale egg is best: some artists even consider a rotten one necessary, but I have always found that a savoury one answers equally well. Nothing but experience can teach you the exact quantity of egg to use. The nearest direction I can give you is to mix your powder white with the egg until it attains the consistency of thick tube oil colour. With a little experience you will soon feel when it is right -that is to say, when you have sufficient egg to act as a cement for your colour without rendering it when dry so hard as to be non-absorbent and brittle. If you wish to lay your colour thinly, or if during use it becomes from evaporation too thick to work, do not add more egg, but reduce it by adding a little water, or, better still, French white vinegar and water. Experience must also teach you how thick to lay your ground, and whether to arrive at this thickness in one coating or two. All this depends much on the individual manner of working.,