Glue sizing and oil priming is the traditional method of preparing canvas for oil painting. The size is made by dissolving 8 level tablespoons of rabbit skin glue in 1 litre of cold water. Soak until all the water has been absorbed by the glue to a porridge consistency, (1 hour or overnight). Then stir and heat gently in a double boiler until the glue dissolves (do not boil the glue). Apply when still warm (not hot) with a stiff brush onto stretched linen or cotton duck. Size acts as a penetrating liquid to fill the pores of the canvas and to isolate the fabric from subsequent applications of primer and oil paint.