Abstract: The method of preparing dried asymmetric cellulose acetate blend membranes through the use of at least one drying agent which is a hydrophobic organic compound, such as polysiloxanes, hydrocarbons, ethers, ketones, chlorohydrocarbons or nitrohydrocarbons. The membranes are dried from their aqueous state by direct evaporation of water. The resulting air dried membranes are suitable for the desalination of water by reverse osmosis, non-aqueous liquid separation, ultrafiltration, pervaporation, and for the separation of various gaseous mixtures into their constituent parts.