When the sizing has been executed on the canvas in good condition, the next thing to think of is the wrong side of the canvas, which also requires a sizing impervious to water and oil, so that the excess of oil coming from the colours shall not go through the tissure, as that might burn it, and so that dampness shall not be able to penetrate it, as that might cause it to rot. This sizing must also be supple, so that the canvas may roll up easily. Many substances may fulfil those requirements -indiarubber dissolved in petroleum, wax and resin, gum lac. But what is yet better, especially for canvas of small dimensions, undesirable to thick too much, is to put two coatings of water-colour fixative. , ,, ,