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Soft Binder Syndrome and Sticky Shed Syndrome

Filed under: storage-care-handling,Tape Aging — 2007-03-21 by Richard L. Hess — Last Edit 2009-01-30 by

For a current list of degrading analog tapes, click here.

For several years, we have been discussing the differences between Sticky Shed Syndrome (SSS) and Loss of Lubricant (LoL). It appears from my latest research (presented at the 2006 Audio Engineering Society’s 121st Convention in San Francisco in October) that LoL does not really factor into the equation for most tapes and that an overarching failure mode is Soft Binder Syndrome, or SBS. Sticky Shed Syndrome appears to be a subset of SBS.

The classic recommendation for tapes suffering from SSS is to bake them and, for now, the continued recommendation is to bake tapes for which baking works. These include:
Agfa (pre-1990): PEM 468, PEM 469
Ampex/Quantegy (1970s-1980s): 406, 407, 456, 457
Note: Recent reports indicate that these problems may exist in tapes made in the 1990s
and later, even under the Quantegy name.
Audiotape/Capitol (early 1980s): Q15
Note: This tape may or may not respond to baking. Some tests will be conducted soon.
Scotch/3M: 226, 227, 806, 807, 808, 809
Scotch 250 has also exhibited some tendency towards SSS

For a current list of degrading analog tapes, click here.

Baking (or incubation) times are getting longer, and 12 hours is not uncommon for 1/4-inch wide tapes. Some tapes need to be re-baked after partial unwinding due to centre-of-reel increased inter-layer pressures. There is some discussion of pressures and tensions here.
If these are squealing and leaving significant deposits, they should be baked (at your own risk). The now-expired Ampex patent for baking tapes can be found here. Almost all SSS tapes are back-coated tapes and the interaction between the magnetic coating and the back coating may be part of the problem.

Tapes which squeal (and generally leave less of a deposit and are generally not back coated) appear to be suffering from SBS. SBS appears to be a change in the glass transition temperature of the magnetic coating. The glass transition temperature (Tg) is the point where the plastic turns from smooth to rubbery. If the Tg falls below the temperature of the head (slightly above room temperature due to friction and player heat dissipation) then the tape is likely to squeal. Small deposits of magnetic coating on the head or other fixed surfaces will exacerbate the squealing. Of course, the drop in Tg is not an isolated phenomenon, but rather a symptom of serious binder degradation.
Lowering the temperature of the playback environment will permit successful playback of some tapes suffering from SBS. We currently have a dedicated refrigerator with both a reel and cassette machine inside. Others have reported success in using an outside balcony during cool/dry weather.

Baking a tape that generally exhibits SBS (and not SSS) may exacerbate the condition and it is not recommended to bake suspected SBS tapes.

Tapes which appear to be suffering from SBS include:
Scotch/3M: 175 and Melody 169 (a seconds brand of Scotch)
Sony: PR-150
Pyral: (type numbers unknown for this French tape)

For a current list of degrading analog tapes, click here.

We have seen cassette tapes also suffering from SBS. These were generally made from pancakes and the tape type is unknown.
As an alternate, you might try Marie O’Connell’s tried and true method shown here. In this case, it appears that the isopropyl alcohol is acting both as a lubricant and as a coolant, and may be also acting as a solvent to remove or inhibit deposits from the tape onto the fixed surfaces.

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