- Jeffrey Martin
Medium utilizing oxidized metal particles carried on a flexible substrate, in order to record an electronic signal, most commonly in the form of audiotape or videotape. Magnetic tape is also used in computers for the storage of data, but this usage is unlikely to be encountered in an art conservation context.
Magnetic recording tape generally is made up of a plastic film base (most tapes, including all videotapes, have a base of polyester terephthalate (PET)), coated on one side with a binder system containing oxidized metal particles. Often, recording tape will also have what is known as a backcoating on the reverse side, which reduces friction, dissipates the buildup of static electricity, and allows for the tape to be more evenly wound. Some early audiotapes had paper backing, while others may also have a backing of acetate plastic, which is subject to the same deterioration factors as acetate photographic film, including so-called ‘vinegar syndrome’. The binder layer, the most critical component of the recording tape, usually consists of metal particles suspended in a binder of polyester and polyurethane, although it can contain numerous other chemicals. Different manufacturers have used different binder formulations, and changed them frequently over time. For this reason, some tapes may be more subject to deterioration than others of similar age and format. In the 1980s, manufacturers began to produce tapes with no binder polymer, but instead a very thin layer of metal alloy evaporated onto the tape base, known as ‘metal evaporated’ or ME tapes. The binder system may also contain lubricants designed to minimize friction as the tape passes through a recording or playback device....