Restoration Tips & Notes Working with audio media (mostly tape) restoration


-Degrading Tapes

Filed under: — Richard L. Hess @ 23:32

Last updated 2012-02-26

This page supersedes the blog page for a listing of tapes that have degraded in some way or another. This page is a list of tapes that we will attempt to keep current. For detailed information see the author’s 2008 ARSC Journal article on tape degradation (click here).

Remember that all of these degradation modes are triggered by a combination of one or more of the following:
–original formulation
–batch variations including incomplete reactions during manufacture
–storage history over the tape’s life (temperature, humidity, pollution)

[added 2012-02-26] One fascinating perspective is emerging from ongoing discussions on the Association of Recorded Sound Collections email list (ARSC List): different tape types in different parts of the world may behave differently. Again, this comes down to plant-to-plant variations at least and perhaps formula and/or raw material differences. A factor that may have caused the differing formulations could be different local environmental regulations for each plant, but that is mostly conjecture on this author’s part, although there were some studies from Alabama attempting to address the pollution from the Ampex/Quantegy plant in Opelika.

[added 2012-02-26] The remainder of this update focuses on Agfa PEM 469, see notes below.

Classic Sticky Shed (Sticky Shed Syndrome or SSS)
(generally responds to incubation/baking)

Caution: Playing a tape with advanced SSS can rip the mag coat off the base film and leave it attached to the backing. If in doubt, it is MUCH safer to bake a potential SSS tape than play it. This especially true as the SSS effects are often worse at the centre where the pressures are higher.

The Ampex Tape Baking patent is available here.

Ampex/Quantegy 406, 407, 456, 457 (1970s-1980s)
Note: Reports indicate that these problems may exist in tapes made in the 1990s
and later, even under the Quantegy name.

EMTEC SM911 As of 2009-01, there are two confirmed reports that 2003-vintage Emtec SM911 is showing the first stages of SSS. A short bake seems to help it. We don’t yet know for how long before it reverts. I hope RMGI has fixed this! Later reports indicate that this may be shed only, without the stickiness AND that it was limited to one or two batches which were mostly replaced. As of this writing, it has been confirmed that batch number B0134007 was involved. This tape may be better placed with the Agfa, below, under non-sticky shed. Please do not assume that either the prior BASF tape nor the later RMGI tape of the same part number suffers similar issues. We do not know how extensive the EMTEC issues are. As of now it seems to be very limited.

Audiotape/Capitol Q15 (early 1980s) Note: This tape may or may not respond to baking.

Scotch/3M 226, 227, 806, 807, 808, 809, “Classic”, and “Master” are the primary SSS tapes

Scotch/3M 250 has also exhibited some tendency towards SSS

Scotch/3M 908, 966/986, 967, and 996 has as of 2009-01 been reported with some instances of SSS. Many other reports do not show this. Looking at the list of 3M tapes on the AES website (click here), and especially the binder types, can provide some help in understanding the progression of failure from SBS to SSS. Seeing the groups there can help predict the performance of a tape not listed above (or below under SBS)

Sony ULH-72-370-BL (stock number X-2441-247-0) was reported by John Schroth at Media Transfer Service in Rochester, NY. This tape responded to baking.

Lighter edge-shedding
(generally responds to wiping)

This section was added 2011-03-05 but represents several years of experience with this variant on the SSS degradation. This type of degradation presents some evidence of classic SSS,  but the main difference is that it is not as far advanced and it seems to be much worse at the edges of the tape than in the middle. This may be an interaction between the binder/mag coat and the air.

Tapes with this degradation modality can be played well after a wipe with Pellon. This procedure can be integrated into the rewind process for tapes which are tails-out. A strip of non-woven,  non-fusible interfacing fabric like Pellon-brand can be cut into approximately inch-wide strips on an office paper cutter (using several folds of material. That is then wrapped around a dowel or pencil and then held so the mag coat runs over the smooth surface. The “tail” follows the tape direction and the fabric is slowly unwound. Generally two or three inches (5–8 cm) is adequate for a 20-minute album side at 15 in/s.

One wipe substantially reduces the risk of some of the edge degradation products lodging on the head and increasing spacing loss (which affects higher frequencies more).

Scotch/3M 201 shows this behaviour. This is the first “low noise” tape from 3M and was available in 1.5 mil acetate (201), 1.5 mil polyester (202), and 1.0 mil polyester (203). So far, I have seen this problem only with the acetate-based version (201), but it is worth checking the polyester versions (202 or 203) for this degradation modality. Obviously, the acetate version could not be baked and this was the impetus for searching for a reliable method of addressing 201.

Scotch/3M 206/207 shows this behaviour on a limited basis, based on poorly stored samples. This tape is starting to get a bit stiffer than when new and reports are coming in that wiping it will remove the edge shedding and allow a good transfer. This shedding, of course, can get lodged between the tape and head and increase high-frequency spacing loss.

EMI Tape (with black mag coat and a dull red back coat) from circa 1973-1974

The difference between this modality and the back coating turning to powder and causing spacing loss is that the residue from this degradation, while much less in quantity and density of a classic SSS tape is still slightly sticky and not a loose powder. In other words, it needs to be cleaned off, not blown or vacuumed off.

Soft Binder Syndrome (SBS)
(generally responds to cold playing)

In advanced states, this condition results in a squeal, but does not have the huge amounts of gooey shedding of classic SSS or even the lighter edge-shedding. Cold playback works in many cases, but playing with a lubricating film of decamethylcyclopentasiloxane (also known as cyclomethicone and )D5 also works well. Marie O’Connell’s wet playback system also works well.

Melody 169 (a seconds brand of Scotch)

Scotch/3M 175

Sony PR-150

TDK 150H (Thanks  John Schroth at Media Transfer Service in Rochester, NY–he used the O’Connell Wet Playback method on these, so it is uncertain if cold playback would work.)

Some unknown bulk-loaded cassettes do respond to cold playback. A few do not but may be coaxed into playback via lubrication with D5 (see our ARSC Journal paper for more details).

Note that the concept of “Loss of Lubricant” is still widely discussed but, as of yet, in polyester-based tapes with polyester-polyurethane binder systems, we have yet to see any documentation that the lubricant is actually disappearing. We had some Sony PR-150 tested and it showed what appeared to be a normal lubricant load.

Pyral (type numbers unknown for this French tape-does not respond to baking may respond to cold playing) Note that as of 2011-12, Pyral has taken over the RGMI

Agfa Tapes
(updated 2012-02-26)

Agfa PEM-526 exhibited dry shedding. See our article here. This is a totally dry dusting of powder, so it may or may not be Soft Binder Syndrome (SBS), but we could class it as that as the particles are not being retained well. Although a similar condition has been reported with PEM-469, recent experience shows a different degradation modality for PEM-469.

Agfa PEM-468, PEM-469 There are mixed reviews on these tapes and we have been told that most of the bad tape was recalled and transferred at Agfa’s expense. This was supposedly affecting only a half-year’s worth of batches from pre-1990. Unike Ampex/Quantegy, baking is NOT recommended as a matter of course, based in part on our experience with the PEM-526 and this article, although the baking temperature may have been a bit too high (60 °C) in that instance.

The author of these pages encountered two very nasty reels of one-inch Agfa PEM 469 in 2012-02 (recorded in 1988-01) that shed a waxy clear-to-slightly-yellow exudate from the mag coat. This waxy coating did show some buildup, especially during fast wind, but not nearly as much as Ampex 456.We can’t call it SSS because one of the definitions of classic SSS is that it is resolved by baking. This apparently is made worse by baking…and I’m too chicken to try it. It should probably be considered yet another variant of Soft Binder Syndrome (or SBS).

Another point of interest is that some of the mag coat was also transferring slightly to the back coat which was then coming off on the capstan (which presses against the back coat side of the tape). This was a pressure transfer from the back coat to the capstan as the pinch roller (pressing on the mag coat side) was segmented and the segments clearly printed onto the capstan. No pressure, no mag-coat residue. This is an A-wind machine, a Sony APR-16. It is a reverse configuration from the Studers.

After consultation on the ARSC List and receiving replies from Marie O’Connell in New Zealand and Corey Bailey in Los Angeles, I decided to continue with the non-baking recommendation as there was just too much conversation on the Web and ARSCList against baking to make me feel comfortable.

The tape’s mag coat was run over a Pellon pad in library wind and then over a D5-soaked Pellon pad, also in library wind.  D5 was generously applied to the heads and fixed guides immediately before the transfer. We applied about 2.5 ml (cc) of D5 to each tape. Note D5 is also known as decamethylcyclopentasiloxane, Siloxane D5, CAS # 541-02-6, and sometimes referred to as Cyclomethicone (generally in regards to the product as produced by Dow Corning). It is found in many personal care products and has recently been declared safe for the environment by the Canadian Ministry of the Environment.

The worse of the two tapes was stopped twice to re-clean the heads and reapply D5. It is not clear to me if the slight loss of brightness was due to reproduce or recording issues, as apparently some batches of this tape shed when originally manufactured.

This tape has been reported stable in parts of Europe, but Ms. O’Connell confirmed the clear-to-yellow waxy exudate and indicated that it was one of her least favourite tapes to transfer. She reported that it did respond to her isopropyl drip technique and Mr. Bailey suggested gentle baking (about 48 °C for 24 hours) which allowed him to have success with the tape.  He also reports success with lubricants from The Last Factory here (second to last section).

Vinegar Syndrome (Acetate Tapes)

This category is different from all of the above. The above refer to variants on polyester (PET/Mylar(tm)) basefilm tapes with polyester-polyurethane binder systems. These tapes are acetate-based tapes and here the rule is DO NOT BAKE! Most of these tapes are from the 1950s and 1960s, though some were made in the late 1940s, and acetate tape was made into the early 1970s. Any acetate tape can suffer from vinegar syndrome, and it is discussed in more detail in my ARSC paper with references to research conducted on acetate film. The listing here are for the worst players that I have come across or heard about.

This search of my blog will provide a listing of related articles.

Kodak Acetate- & Durol (Triacetate)-based tapes are the primary acetate tapes that we continue to see suffering from vinegar syndrome.

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