TOP: Typical video tape construction. BOTTOM: Typical VHS Tape path, courtesy howstuffworks.com
Video tapes have a large and special set of longevity problems, apart from traditional chromogenic photos. And while their imaging clarity was never as good as most photographs to begin with, these memories, often home videos, need to be protected, too.
Video tapes--the VHS, SVHS, VHS-C, and Hi 8 that most of us have been using for years--are fundamentally composed of three layers: the binder layer, the substrate, and the backing. While there are many differences from manufacturer to manufacturer, the engineering of these layers is a result of a very special need that video tapes have that photos don't, which is to survive the friction and stress of repeated playback, winding, and re-winding.
The binder layer comes into direct contact with the heads of the playback machine, and is responsible for signal quality. It contains magnetic particles (sometimes referred to, a bit anachronistically, as pigments, even though they are usually iron oxide) that store information on the tape. They are usually suspended in the binder along with lubricant, whose purpose is to seep out during playback, microscopically speaking, and prevent damage to the binder layer by the drum and head of the playback machine.
The substrate and backing layers are there for dimensional stability and strength, since the binder layer itself is quite thin. The backing in particular also helps with reducing friction.
An example of a completely delaminated video tape. The binder layer (brown) has separated from the backing. Source: Anothermelbournite
VHS, VHS-C, SVHS, Hi 8, Digital 8, and even DV all share one thing in common: they are magnetic media. And the trouble with magnetic charge ("remanence") is that it is fundamentally impermanent. But that's just the beginning of the trouble for video tape, for there is a long list of ways it can deteriorate:
There is no shortage of claims that video tapes "won't last 10 years", almost always from services promoting VHS transfer to DVD! The truth is more subtle, and is suggested by a considerable body of longevity research done specifically on a wide range of video tapes by the National Media Laboratory, Jet Propulsion Labs at Cal Tech, the National Bureau of Standards, The Advanced Development Corporation, and manufacturers Sony and Fuji. First, the risk of hydrolysis, which is potentially catastrophic, is substantially related to how well you store your tapes (see below). Second, the research generally indicates that magnetic tapes (like VHS, VHS-C, etc.) stored well, will experience 10-20% signal loss, purely from magnetic remanence decay, after 10-25 years. While losing 20% is not losing the the entire picture, it may well be the difference between enjoying a memory and simply displaying it. So the sooner your video tapes are digitized, the more signal can be preserved.
In case you can't get your video tapes digitized now, you have some choices about how to store them in the meantime:
20%Upper end of video signal loss for a well-stored video tape after 10-25 years.
5 The number of years ago that a major Hollywood movie was released on VHS. This last release on the format was the 2006 release of "A History of Violence."
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