Magnetic tape

Magnetic tape emerged from a peculiar convergence in 1920s Germany, where a chemical engineer who coated cigarette papers with metal realized he could magnetize sound itself. The invention was inevitable the moment three conditions aligned: Valdemar Poulsen's 1898 telegraphone proved magnetism could capture sound, the chemical industry learned to coat substrates uniformly at scale, and broadcasting created demand for pre-recorded content indistinguishable from live performance.

The foundation was Poulsen's telegraphone, demonstrated at the 1900 Paris Exposition where it recorded Emperor Franz Josef of Austria's voice—the oldest surviving magnetic audio recording. The Danish engineer's device magnetized steel piano wire moving at 84 inches per second. But wire had fatal limitations: expensive, prone to tangling, and requiring speeds that made editing impossible.

By the 1920s, three enabling technologies had matured: cellulose acetate film, lacquer chemistry, and Germany's advanced chemical engineering. Fritz Pfleumer, working on coating cigarette papers with metal strips, recognized in 1927 that he could apply the same technique to create "sound paper." He replaced bronze powder with iron oxide suspended in lacquer and coated 16mm paper tape. On January 1, 1928, his German patent was granted.

On December 1, 1932, Pfleumer licensed his patent to AEG. Nazi Germany's state radio network needed pre-recorded propaganda that sounded live. BASF in Ludwigshafen began intensive research, replacing paper with cellulose acetate film. Eduard Schüller developed the ring-shaped magnetic head in 1933. The Magnetophon K1 debuted at the August 1935 Berlin Radio Show. In 1939, BASF replaced Fe₃O₄ with Fe₂O₃—a formula that became the worldwide standard. Combined with AC bias, the sound quality was so perfect that even audio engineers couldn't distinguish recordings from live broadcasts.

The technology would have remained German if not for U.S. Army Signal Corps engineer Jack Mullin, who discovered a Magnetophon at Radio Frankfurt in 1945. When Bing Crosby heard Mullin's demonstration in June 1947, he immediately placed a $50,000 order with Ampex. Germany's defeat had voided the patents, giving America a 20-year advantage.

Computing followed immediately. Magnetic tape was first used to record computer data in 1951 on the UNIVAC I. IBM's Model 726, announced May 21, 1952, could store 2 million digits per tape. A single 2,400-foot IBM 729 tape stored the equivalent of 50,000 punched cards.