A lot of analogue tape manufactured in the mid-to-late 1970’s is starting to come out of storage for remixing and re-issue and engineers are finding that in some cases the tape won’t play. In these situations, tapes can exhibit a tendancy to squeal or stick to the guides and heads in the recorder’s tape path. In severe cases the tape may be sticky enough to even stall the transport.
Here’s where the stickiness comes from. The binder is the chemical compound that holds the oxide particles together and sticks them to the tape backing. Under humid conditions (which means anything other than controlled low-humidity storage), the polyurethane used in the binder has a tendency to absord water. The water reacts with the tapes’ urethane molecules causing them to migrate to the surface of the tape where they gum up the tape path during playback, leaving a dark gummy residue. However, this effect is temporarily fixable by a controlled heating (baking) of the tape involving a process pioneered by Quantegy (formerly Ampex).
For the baking process, there are several kinds of ovens you can use. One thing you DON’T want to do is stick it in your kitchen oven and turn the heat on “low”. Most oven thermostats don’t go low enough, don’t provide a stable enough temperature control and a gas flame generates quite a bit of water vapour which is exactly what you’re trying to get rid of. The tape, after the controlled baking treatment, will remain playable if stored in a typical room enviroment for approximately 30 days, enabling a transfer onto new medium. Providing the heating process has been applied before too much oxide has been initially dragged from the tape’s surface, there will be no loss of output or spoilt EQ.
It should be emphasised that today’s analogue tapes use state-of-the-art binder systems and formulations that offer much improved archival stability. Even so, the utmost care should still be taken to provide proper temperature and humidity control in areas where valuable master tapes are stored.
Photo: Adrian Boot, Fifty-Six Hope Road Music Ltd
Hot, humid Jamaica may be a great place for a holiday but it’s not the ideal place to store audio master tapes, especially if they contain irreplaceable and previously unreleased live recordings of the legendary Bob Marley.
Under such conditions, and without the benefit of reliable air conditioning, old analogue tapes can quickly get themselves into a very sticky situation. The oxide sheds, the spools rust and various unpleasant moulds make themselves at home on the tape surface.
This was precisely the situation Bob Marley’s wife, Rita discovered when she unearthed 27 × 2-inch analogue masters that had been languishing in the family archives for more than 25 years. The tapes, which included live recordings of Marley at the Hammersmith Odeon and Lyceum in London during the early 1970s, were literally falling apart and needed careful handling if any of the original material was to be salvaged. Cleaning and copying them became a priority, not only to rescue the recordings but also because Island Records wanted the material for a new live album that will form part of a Marley retrospective later this year.
The Copyroom became involved in the saga when Rita Marley, along with Roy Parsons from RPL Ltd and Marley’s engineer Erroll Brown, called for advice.
“They were in a truly dreadful state,” says Copyroom manager, Kev Vanbergen. “I’ve never seen tape in such a mess – it just goes to show what damage humidity can cause over a long period of time.” With the help of copyroom engineer, Pascale Giovetto, Kevin spent an entire week manually wiping the dirt and mould from the tape surface and hand winding it onto new spools. The recordings were then transferred onto requested DA88 tape.
He adds, "As part of our research into how best to salvage them, we spoke at length to Jonathan Lewis at Quantegy and to Metrum, a specialist company in the Midlands that carry out restoration work for the Ministry of Defence. Even with their help we were only able to rescue 12 of the 27 spools, giving about six hours of recorded material.
The remainder, which may sadly be beyond repair, were handed back to Rita Marley when she returned to listen to the recordings. She was delighted with the result and thanked Kevin and Pascale for all the hard work that theyâ€™d put in. "It’s very emotional for me to listen to these tracks again, she added.
Trying to play old tapes that haven’t been through the ‘baking process’ can damage your tape machine by putting excess stress on the motors and transport. Also the tape output will quickly deteriorate as the oxide is lifted from the tape.