Magnetic Tape Deterioration and Data Recovery 2. TAPE MANUFACTURING PROCESS Magnetic tape comprises a magnetic oxide coating on a polyester backing tape, held in place by a binding agent. The binder also contains lubricants to prevent damage to the tape heads as the tape passes over them. The same principle also applies to 3480 cartridges, the tape simply being encased in a plastic cartridge. Rapid and dramatic increases in the volume of data generated from seismic surveys has lead tape manufacturers to produce a tape which will hold more data. In the 1960s and early 1970s, the standard recording media was 21 track one inch wide tape, containing 356 or 712 bytes of data per linear inch. By the early 1980s the common recording media had become 9 track half inch tape, recorded at 6,250 bytes per inch. In the mid-1980s and through the early 1990s, 3480 cartridges became the standard media, recorded at over 30,000 bytes per inch. Clearly the density of recording has increased dramatically, and there have been various changes in the composition of the magnetic oxide and the binder as manufacturers strive to produce tapes with higher recording densities. Some compositions have not been as successful as others. Chromium dioxide tape is used in 3480 cartridges, and some tapes in early cartridges deteriorated substantially because the original binders proved to be unsuitable for use with chromium dioxide. The binder reacted with the chromium dioxide releasing gas which became trapped in the binder, causing more gas to be released and more deterioration of the tape. The speed of tape drives has increased from 25 or 45 inches per second in the 1960s up to 125 or 150 ips in the 1990s. This resulted in more wear on tape heads, which caused manufacturers to produce tapes with lower abrasivity. However, at the same time tape head manufacturers were addressing the problem of head wear by designing harder wearing, ceramic coated heads instead of the older chromium plated heads. Ceramic heads are much more abrasive to tapes, and the consequence of using a low abrasive tape on a high abrasive head is increased tape damage. One leading tape manufacturer acknowledged this problem in the late 1980s and stated that the life of a tape designed to be used with chromium plated heads (as their brand of tapes were earlier in the decade) would be shorter when used with ceramic heads. By then, of course, large quantities of seismic data had been recorded on the "wrong" type of tape for the current tape heads. Table of Contents INTRODUCTION TAPE MANUFACTURING PROCESS TAPE DETERIORATION DATA AUDIT DATA RECOVERY SUMMARY See other technical papers.