How phonographs records are made, Popular Science 1947 – “THE silent black disk that makes noises when needled is chiefly shellac, lampblack and limestone. In its manufacture, however, pure gold, wax, glass, copper, nickel and sometimes chromium are used by the craftsmen who operate the intricate and delicate machines that squeeze sound into a scratch. From beginning to end, the commercial manufacture of records is a tremendously exacting process. For example, 50 percent of the wax-coated glass disks on which the music is recorded are rejected before reaching the cutting room. The accompanying pictures tell the story.” – Link.