Among the more than 1,000 patents bearing Edison's name are several for vacuum coating processes. In 1894 Edison was granted a patent on the "Art of Plating One Material on Another." The patent described coating by evaporation in a vacuum by direct resistance heating or arc heating, using a continuous current. Edison called the process "electro vacuous deposition." He prophetically wrote that "the uses of the invention are almost infinite". Edison also employed sputter deposition. In 1900, Edison applied for a patent on a "Process of Coating Phonograph Records." Issued in 1902, the patent describes using a "silent or brush electrical discharge" produced by an induction coil. Edison had found a way, perhaps accidentally, to use high-voltage alternating current to deposit a metal; the pressure was higher and deposition was by sputtering rather than evaporation. The National Phonograph Company, one of Edison's many enterprises, used the sputtering process to deposit a thin layer of gold on wax phonograph cylinder masters that could then be electroplated to form molds to mass-produce celluloid duplicates. The resulting cylinders were touted as "Gold Moulded." The method was used for 20 years, from 1901 to 1921. It enabled the reproduction of cylinder grooves less than 0.001-inch deep at a density of 200 grooves per inch. From 1913 to 1921, 10-inch-diameter Edison Diamond Disc phonograph records were made using the same method. Sputtering was abandoned as it could not be scaled up to produce the 12-inch discs that were introduced in 1927.