Ampex was not alone. During World War II, Semi Begun at the Brush company developed a ring-type recording head under contract with the Office of Scientific Research and Development. This ring worked best with coated tape and with Gerard Foley of the Batelle Memorial Institute developed paper and acetate tapes coated with alnico and magnetite powders. Brush approached a number of companies, including the Minnesota Mining and Manufacturing company, to manufacture the tape. In 1944, Ralph Oace at 3M solved the problem of coating a paper base with the magnetite powder, but the war ended the funding for the project. The Shellmar company manufactured the paper magnetite tape in 1946 for the Brush Soundmirror tape recorder and also a 5-inch magnetic disk for the Brush Mail-A-Voice disk recorder that sold for only $40. The experiments of Oace and the FIAT reports of the German BASF tapes caused the 3M company to create a magnetic tape laboratory in 1946. This lab discovered that needle-shaped acicular particles of gamma ferric oxide produced better coercivity (350 oersteds) than the cube-shaped particles of magnetite used by Brush (150 oersteds). 3M introduced the Type 100 paper tape (black oxide) in 1947, and the popular Type 111 acetate tape (red oxide) in 1948 that Bing Crosby used to record his Philco show with the new Ampex 200 tape recorders. By 1948 the American tape recorder industry was firmly established. The Magnecord company introduced the PT-6 professional recorder for $750, far less than the Ampex models, and a stereo model in 1949.
Begun Chapter 6
