Sticky Shed Syndrome

My previous blog post was all about the Vinegar Syndrome that can be found in some types of acetate audio tapes. An even more pervasive issue with open reel tapes is “Sticky Shed Syndrome.” The following will discuss what it is, the cause of it, and how we deal with it from a preservation standpoint.

Sticky Shed Syndrome is a problem in high-output tapes manufactured from the mid 70’s to mid 80’s. One can detect that a tape is suffering from this issue if, upon playback, the tape produces a squealing noise, leaves behind sticky residue on the contact points of the tape machine, and/or slows the playback speed of the tape. This is a serious problem because not only does it make the tape unplayable in most instances, but doing do causes severe physical wear to the tape.

Tape is constructed in layers, consisting of a layer of magnetic oxide particles that contain the audio recording, held to a substrate layer of polyester (or some other material) with a binder material. There is sometimes a back coating layer which consists of carbon particles held to the substrate with another binder layer.

The cause of the shedding issue is a reaction called hydrolysis. Basically, the tape binder is absorbing water from humidity in the air, causing the magnetic oxide particles to separate from the substrate. The loose oxide particles easily shed off the substrate upon playback in this condition.

To explain this reaction in more chemical terms, I will reference a recent publication by Sarah Norris in the ARSC Journal, Vol 41, No. 2:
“The polyester polyurethane binder used in audio tape is formed by a reversible chemical reaction, esterification. In esterification, a carboxylic acid and an alcohol react to form an ester, with elimination of water. Hydrolysis is the reverse of esterification. In this reaction, water breaks the ester linkages to reform the carboxylic acid and alcohol. In the hydrolysis of polyester polymers , not all the ester linkages are broken. Instead the reaction produces smaller molecule segments with both acid and alcohol ends.”

In dealing with this issue from a preservation standpoint, there is a short-term solution to the problem used by audio engineers called baking. Baking involves putting the tape in a controlled, low-heat oven or food dehydrator for a period of time. This process removes moisture from the tape, and effectively makes the tape temporarily playable again. It allows us to get a successful digital transfer without damaging the original tape.

To explain the chemical reaction of the baking process, I will again reference the Norris article:
“One study says that baking reverses hydrolysis, thus re-forming ester linkages and reassembling binder molecules (Bertram & Cuddihy, 1982). The elevated temperature and relatively low humidity, RH, inside a hot oven drive excess moisture from the tape, creating an environment in which binder hydrolysis can be reversed, stickiness reduced, and playback performance improved. These effects are understood to be temporary because hydrolysis resumes after baking, presumably proceeding for several weeks until a critical mass of binder re-degrades and the tape again becomes unmanageably sticky. High temperature and low RH work together to reduce the tape’s water content through processes of evaporation and equilibrium.”

Now for a walk-through of the baking process, with pictures:

This is the problem tape that we are dealing with: an Ampex 407. This type of tape is well known for developing problems with sticky shed.

The tape must be wound from its original 7" EIA reel to a 10.5" NAB reel. This prevents physical deformation of the tape during baking due to tight winding of the tape near the center.

I then must remove the metal flanges from the hub. We want to avoid holding a lot of heat in close proximity to the tape to prevent melting the plastic. Additionally, removing the flanges allows for more air flow between the tape pack during baking.

The tape is then placed into a tray of the food dehydrator for baking.

I generally bake 1/4" tape for 4 hours at 130 degrees Farenheit. I flip the tape every half hour to ensure that it heats evenly. And no, I don't make dehydrated fruits and vegetables in this food dehydrator!

The tape is ready to be baked. I have had many successes using this method for dealing with sticky shed syndrome. There are no standardized tape baking times, so if 4 hours isn't enough, then one can put a problem tape back in for additional time.

Finally, the tape is left for a 24-hour period to return to control room temperature and is transferred back to the correct size reel before being played back. If problems persist, the tape will go back into the food dehydrator.

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Vinegar Syndrome in Tapes

My big challenge for the day has been to figure out how to handle a tape suffering from what is known as “Vinegar Syndrome”. The tape is a 7″ Kodak 31A Sound Recording tape on Triacetate backing.

Box for Kodak 31A Triacetate tape

This particular make of audio recording tape has a reputation for generating a strong smell of vinegar, due to hydrolysis. This chemical process causes acetic acid to formulate, which deteriorates the tape. This same chemical process has been a huge issue with Kodak “safety tapes” in the film industry. I found a statistic, copied below, to give you an idea of the severity of the problem:

“Film archivists have estimated that a whopping 75% of all U.S. silent
films have been lost through deterioration or improper storage
procedures, and that 50% of all films made prior to 1950 are
gone. In addition, many much more recent works lie in vaults,
wasting away to the point where the negatives have become
corrupted.”

The vinegar syndrome problem is a product of the original tape’s composition combined with the storage conditions in which it was kept over the years. This tape was stored in a plastic bag within the cardboard tape box.

The tape box with plastic bag in which it was stored.


While one may think that the plastic bag would help to keep moisture away from the tape and prevent hydrolysis from occurring, it actually acts to hold in acetic acid gas released during the chemical process. It is an autocatalytic reaction, which means that the acetic acid produced actually causes the reaction to happen at a faster rate. In effect, the problem becomes worse by keeping the tape in a plastic bag with the air that smells like vinegar.

Besides the smell, this tape also showed very bad warpage and cupping. Acetate tapes can become very dried out and brittle. The physical deformation combined with the chemical breakdown puts this particular tape in very bad condition.

Tape coming off the original reel to the tape guide arm. You can note it's physical deformation. Tape usually will make a flat, taught, smooth journey from the original reel, around the tape guides and heads, and on to the takeup reel. You can see that the severe physical deformation here had a comparably rough journey.


Another shot of the deformed tape; this is between the tape guide arm and takeup reel.


This video shows the severity of the tape warpage as it is played back on the machine. You can see that the takeup side has less severe after moving through the tape guides and heads.


This video is a closeup of the tape as it passes over the reproduce head. You can see that the tape curls in at the edges and does not always make full contact with the play head. I was able to make a transfer, but at a lesser quality, because the tape did not lay flat.

After playing back the reel, I found that the tape pack on the takeup reel was very loose and uneven. Trying to fast-wind the tape back on the original reel was unsuccessful and resulted in bumps and an uneven winding.

You can see visible space in the tape pack. This is problematic for storage, and can cause even more damage to the tape, especially on the edges.


I ended up playing the tape back at the 7.5 inches per second play back speed in order to get a decent pack, though it was still not great.

The tape will be removed from the plastic bag and put into a buffered, acid-free archival storage box for permanent storage. The buffering acts to neutralize the acetic acid gas that forms, halting any further detriment due to hydrolysis.

It is very important that this transfer work for the collection is happening now. The problems get worse over time, and can become unplayable or inaccessible because the materials themselves have broken down to a point where they become too delicate to play back. This tape is definitely at the end of its usable lifespan. Lucky for us, I was able to make a transfer of the audio recording on the tape. The tape contained a recording of one of Sigurd Rascher’s recitals from 1963. My guess is that it is the only tape of it that exists in the world. Had we waited any longer to transfer it, it may have been lost forever!

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A note from Carina Rascher

Just stopping by to re-post a note from Carina Rascher.

———————————————————————————-
Dear Friends of the Saxophone, 15.Nov.2010

Please support our efforts to restore the vast (488) audio collection that is part of the Sigurd Rascher Special Collection at SUNY Fredonia, NY. The entire estate (manuscripts, over 7,000 letters, instruments, artifacts, photos, notes from 7 decades and much more) will soon be (is) open for public viewing by appointment. You can make your contribution by voting daily for the pepsi grant.

For more information please go to http://www.refresheverything.com/rascheraudio

Thank you.
Carina Rascher

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It’s time to vote!

We were accepted for the November voting period of the Pepsi grant program, as described in the previous post. Please help us out in the month of November to have the most votes for a $50,000 award through the Pepsi Refresh Everything grant. Everyone can vote one time per day, per project, so keep coming back every day of the month of November to support the cause.

You can vote on the website at this link:
http://www.refresheverything.com/rascheraudio

You can also vote directly on Facebook using the Pepsi Refresh voting application:
http://apps.facebook.com/pepsirefresh/idea/set?auth_token=e68b8916e28d5d2e0be25a0d87d8f783

The last alternative is to vote via text. Standard text message rates apply.
Text 103703 to Pepsi (73774)

I am also creating an e-mailing list that will send out daily reminders to vote. Please send me a message at Rascher.Archive@gmail.com to be added to the list.

You can help by spreading the word to all of your friends, family and colleagues! Thank you!

Thanks for your help! Please spread the word!

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Directions for voting on the Pepsi Grant

We are in the midst of many grant applications to secure more grant funding for the Rascher Audio Digitization project. One of the grant programs that we participating in is the Pepsi “Refresh Everything” program. Pepsi is hosting this program throughout the year 2010. Each month, they accept 1,000 applications for review. Upon approval, the project proposals are posted on the Pepsi Refresh Everything website for a one-month period. Throughout the month, everyone (within the U.S.) is invited to view the various projects and vote for the ones they think should receive funding. Each month, there are 32 awards given: two $250,000 awards, ten $50,000 awards, ten $25,000 awards, and ten $5,000 awards. Projects fall under one of six categories: Arts & Culture, Health, Food & Shelter, The Planet, Neighborhoods, and Education.

You can find out more about the program through this link: http://www.refresheverything.com/how-it-works

I successfully submitted a proposal for $50,000 for the Rascher Audio Preservation Project in the October submission period. The application, along with all the other applications in this voting period, is under review. We will be notified on the 1st of November as to whether we were approved. Pending the project’s approval, I will post a link to the page for voting for the project on the Pepsi Refresh Everything website. You can browse through some grant applications for the October voting period through this link: http://www.refresheverything.com/categories/arts-and-culture

Voting is easy; simply navigate to the project page that you wish to vote for, and there is a button that says “Vote for this idea.” Each person has 10 daily votes, and it is possible to sign in using a Facebook account to avoid having to create a new account. It is very important to return and vote every day for the month if you support this idea. This is an extremely popular program, and there will be lots of tough competition in becoming one of the top ten projects at the end of the month. Unfortunately for us, all of our international friends are not allowed to vote in this program. The voting is restricted (by Pepsi) within the United States only.

I will make another post to notify everyone whether we are approved on November 1, 2010. Please share this among your friends and colleagues and encourage them to vote daily to give us a good shot at this grant!

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Creating exact copies of Compact Discs

The latest phase in the project has been creating Archival Safety Copies of the Compact Discs in the collection. One would think, “how difficult is that? Just put the disc in your drive, open up iTunes, and hit import.” Well actually, this type of encoding by consumer software can produce a fair amount of errors. When wanting to make copies of CDs, exactly as they are and free of error, one can use either software: Exact Audio Copy (EAC) or dBpoweramp CD ripper. I chose to use the latter for this project. This software creates secure rips, and gives a detailed report as to any potential insecurities in the rip. It uses a feature called “AccurateRip” to compare your CD rips to other in the database,¬†ensuring accuracy.

You can find out more about the software here: http://www.dbpoweramp.com/cd-ripper.htm

Transferring the mass-produced CDs in this way was most successful, and produced all error-free transfers. However, CD-Rs are notoriously known for not ripping accurately. I encountered some errors with CD-Rs in the collection.

Unfortunately, CD-Rs are not a permanent media format. Especially in the early days of the technology, the dyes used tend to fade over a few years, making the data stored on them impossible to read. Additionally, CD-Rs can have problems with the metal oxidizing around the edge of the disc, if not sealed properly. A lot of the issues with recordable CDs stem from the fact that there are no public standards for the discs themselves and no drive standards for reading or writing the discs. Because of this, there is a lot of variety in quality and composition of disc media, even within each brand. The same is also true of drive – a CD that is readable in one drive may not be readable in another.

There is a proprietary standard for discs called “Orange Book Part II.” This specifies certain details about CD-Rs must be adhered to in production, but does not state a specific dye that must be used, which is a big issue, as the dye is the most important part of the disc. The industry is still split mainly between two types of dye, that react differently when being written. Each type requires different amounts of laser power, and with no drive standard, it comes down to luck as to whether you will get a successful CD-R write.

More information about CD-R and CD-RW media can be found here: http://www.mscience.com/faq.html#CDR

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Overcoming a sticky tape

After many successful cassette tape transfers in the archive, I finally encountered a problem tape last week. This tape was a commercially released cassette, and contained a compilation of music by British composer, Eric Coates. There was a recording of Sigurd Rascher playing his saxophone concerto, “Saxo-Rhapsody.” The playback issue with this tape caused the sound to become warbly. Also, the mechanical playback speed slowed and would grind to a halt as it reached the end of side A.

Initially, I thought it was a problem with the cassette deck. I checked it over, and had my trusted analog equipment repair technician, Greg Snow, check it over. There were no noticeable issues with the deck. There also were no other tapes that had such an issue. Greg recommended that I change out the cassette housing for this particular tape. The felt bumper in a cassette can wear down, and the corner rollers and hubs can become faulty, causing playback issues. I removed the old housing and placed the tape in a brand-new housing from a blank, screw-open cassette tape.

This picture shows the old, unopened housing next to the new housing to which the tape will be moved.

The old cassette has been carefully pried open, making sure not to damage the tape inside.

The old tape moved to the new housing, next to the original housing and case.

Once that process was complete, I put the tape into my cassette deck, to test whether it worked. To my disappointment, the cassette still showed the same playback issues as in the old housing!

I got back in touch with Greg Snow, and he suggested I try the tape in another machine. I played it back in his Luxman cassette deck, and amazingly, it worked! I wondered, why would it have this issue in the first deck, which showed no physical problems whatsoever, but play back fine in the second deck? Greg said, “sometimes the relationship between tapes and decks is like the relationship between people…they just don’t get along.”

That being said, this has been the only tape with which I’ve had an issue, so I can consider myself lucky. In other news, the cassette transfer phase is nearing completion, and we are preparing for the next phase. Stop by this page again for more updates in the near future!

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