Several details are described in the preparation of capillary tubes for x‐ray power specimens which greatly facilitate the synthesis of such tubes and their subsequent removal from the pilot wire. The over‐all method employed is essentially that of Frickeet al.Wires of 22‐gauge copper, after annealing in an atmosphere of helium, are cleaned and dipped into the cellulose acetate solution by means of a crank‐driven rack. The rate of withdrawal determines the wall thickness. A method is given for centering the filled specimen tubes precisely in the powder camera by the use of a centering jig.