a vascular prosthesis is made by wetting a porous polyester fiber tubing with water until it gains close to maximum amount of weight , removing excess liquid from inside the tubing , repeatedly contacting the inside surface of the tubing with a solution of a biocompatible polymer in a water - immiscible solvent to adsorb some solution on the inside surface of the tubing , and removing excess solution , then removing solvent from the adsorbed solution to form a nonporous elastomer coating of the desired thickness on the inside surface of the tubing .