The canvas is first treated with size or a solution of glue; this should be as free from colour as possible. The priming consists of two coats, the first containing whitening and size, the second lead white and linseed oil. Fuller primings are often given where it is not desired to allow the texture of the canvas to remain evident. Such primings are put on alternatively in directions at right angles to one another, and are treated in the same way as the primings of a panel. If before the last priming be dry it be dusted with zinc white, or if a very thin final priming of zinc white and drying oil (free from lead) be given, the usual discoloration of the canvas which occurs on keeping it, especially in the dark, will be avoided. But such discoloration can always be removed by leaving in contact with the priming a piece of blotting-paper saturated with a solution of peroxide of hydrogen. ,