A brief survey of the types of fabric supports and the types, concentrations, and consistencies of sizes used historically. Reasons commonly cited for the necessity of sizes are compared to the degradive effects. The history of the choice of textiles is studied with an emphasis on the repeated selection of linen by artists and conservators. The strength loss of cotton and linen is paralleled with the chemical and physical stability of synthetic fibers. The desirable properties of synthetics are listed. -- AATA