[ Sarah Everts writes about the race to save magnetic tape in the August 21, 2014 issue of NewScientist in Wiped out: The race to save our video heritage. This article suggests that the fix is to convert magnetic tape to digital.  But digital will not last for centuries, and also suffers from the possibility of media that no longer have devices to play them, especially in the future when the electric grid isn’t always up and the consequent inability to make today’s computer chips is lost (also from lack of rare earth metals, etc).  I’ve paraphrased and put in excerpts of this article below.  Alice Friedemann  www.energyskeptic.com ]

What’s at stake

Whether recordings of people speaking near-extinct languages, video documentation of earthquakes in action, footage of Nobel laureates in their labs or defining moments in sport and culture, a goodly portion of recent human memory is encoded on thin strips of black ribbon. The Co-ordinating Council of Audiovisual Archives Associations has recently estimated that worldwide some 200 million hours of culturally valuable audiovisual content is in danger of disappearing entirely if it isn’t converted into a preservable digital format.

Richard Wright, a former technology manager of the BBC archives estimates 70% of content on magnetic tape will be lost within a decade due to slow rates of converting them to digital media.

Magnetic tape begins to degrade chemically in anything from a few years to a few decades, depending on its precise composition.  Often it’s not only the tapes degrading, but also the technical know-how to play them at all, or the machines to play the dizzying 60 plus formats of magnetic tape invented since 1956.  Tapes vary from a quarter of an inch to two inches wide, have differing real and cassette dimensions, and specific playback equipment for each one. Magnetic tapes are made in dozens of ways as well, and manufacturers won’t disclose how their tapes were made even though they’re obsolete now, making it hard for researchers to understand why they’re degrading.

The problem: Magnetic tape suffers from fading magnetism over time and “sticky shed”

The structural base of most magnetic tape is a thick layer of polyester, although in older audio tape it can be acetate, paper or polyvinyl chloride. Whatever the base, information is encoded in a thin coating of magnetic particles embedded in a polyurethane-based binder. In the earliest tapes, these particles were made of iron oxide. Other magnetic particles have since come on the scene. Barium ferrite is less rust-prone and has a smaller particle size, allowing information to be encoded more densely. Chromium dioxide is ideal when a recording has a lot of high-frequency sound.

The range of frequency and volume that a tape can record, and the ease of recording and re-recording, are determined by the size of the particles, their range in size, and their orientation on the tape. Various lubricants make the tape flow smoothly through the player, plasticisers make it supple, and antifungal agents and antioxidants extend its life. There are also other ingredients whose identities are proprietary, says Eric Breitung, a conservation scientist at the US Library of Congress in Washington DC.

A common problem magnetic tape suffers from is “sticky shed”, which occurs when the polyurethane binder that holds magnetic particles on the tape begins to break down and leach out – when stored in humid conditions, for example. Even if the recording remains playable, the tapes can easily get stuck or ripped in machines. The fix is baking them to dry out moisture and restabilize the polyurethane by heating them to  50 °C from hours to weeks.