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Sticky Shed Syndrome and Tape Baking

I've been doing transfers from old sessions for various clients and invariably came across the phenomena known as Sticky Shed Syndrome.

So as I was dealing with transfers I eventually had to modify a small convection oven to do exactly 54C as per the Ampex patent (yep - Ampex knew of this and filed/got a patent on the process). The issue was that most store-bought ovens don't go below 150F so I needed to modify the oven to hit 54C/128F. Since I design this stuff, it was easy for me - I really don't recommend it as a DIY unless you're a seasoned hardware engineer.  But for those that are, it's simply a matter of placing a resistor across the NTC thermistor input of  oven's microcontroller A2D input. Using a calibrated meter/thermocouple, I nailed 128F within a degree or two. Also put indicators across the coils to see when the tiny uC was actually firing the coils.

So as I was doing this, I recently also acquired another microscope for my hot air solder tool that has 1280x1024 resolution for dumping into a PC. Figuring I'd at least try to see if there was a visible difference between tapes that were giving me hell and those that weren't.  I did some before and after shots as well as a photo of what appeared to be a tape that held up well with no special storage - PEM 468.  As an example here's a song that was dumped from a safety master on 468 - no bake required - http://home.comcast.net/~ajawam/sdollar.mp3 . BTW -This was quickly remastered using Wavelab 6.0 with TC Powercore Denoiser, an MD3 and Voxengo Elephant. You can hear the hiss on the one channel as the TC grabs it.
 
This reel also had a section of Ampex 456 spliced in at the tail. As soon as it hit this, it became apparent that it was suffering from SSS after about 2 seconds - the typical squeal. When the tension was relaxed from the supply and take up reels, the tape just stuck to the heads with the tale tale line of melted binder apparent on the tape where it stopped. So this was the candidate I used for the photos.

So what have here is:
- A reel of 1/4" tape that had not been played in over 20 years
- A reel of tape wound tails out with a library pack
- A reel of tape that had both PEM 468 and Ampex 456 both around mid 1980's vintage
- The Ampex section was at the tail, leadered with Scotch plastic leader; about 5 minutes of tape at 15 IPS
- A reel of tape that was not stored in any special vault; exposed to Pittsburgh (for 8 years), New Hampshire (3 years), and Northern Virginia (10 years) climates.

The reel was rewound using custom bypass rollers I had Terry at Terry's Rubber Rollers
( http://www.terrysrubberrollers.com/ ) lathe for me.
The machine is a BR-20T with the torque re-adjusted for minimal back tensions.
Since this machine has idler arms with rollers, the entire fast rewind was via rollers.


A video of the tape path bypass can be found here
A video of a 1/2" TSR8 tape path bypass can be found here


Here's the photos - Click on the photo for a 1280x1024 image
PLEASE NOTE: these samples were clipped from the reel and baked flat on the
flange along with the parent reel, oxide up, about 4" in length.
PEM 468 with no baking

This is the Agfa PEM 468 which shows significant wear. The majority of the reel was this tape, which transferred easily with no baking. Typical dusty shed (slight due to the wear of the tape).
Ampex 456 - Pre-bake

This is from the head of the section, right after the leader.
Ampex 456 - Post-bake

This is the same section of Ampex 456 after a 3 hour bake at 54C.



Many sites that have audio forums mention it, as well as have a lot of misinformation on the issue. A few sites as well are fronted by people that are experts in this - below is a list of links to various ones that have good info on the problem as well as offer services for tape restoration:

Richard Hess:
http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/degrading-tapes/
http://www.richardhess.com/tape/

Xepa Digital:
http://www.xepadigital.com/index1.html

Sonicraft:
http://www.sonicraft.com/guide.html

Some more info here:
http://www.tangible-technology.com/tape/baking1.html


Microscopy of a Newer Batch of Ampex 456

As I was dumping tapes from other studios, I noticed that even some newer batches of 456 were still exhibiting some degree of stickiness, though not to the extent of the above sample. I noted that none squealed, but near the head and the tail they displayed signs of what Richard Hess's ARSC article mentions as SBS - Soft Binder Syndrome.

At the sections right after the discloration near the head and tail (up to approx 2 minutes in), these tapes when stopped would cause a slight line of melted material, with little deposit on the heads or fixed guides - ocassionally sticking only to the playback head and last fixed guide when the tension was removed from the reels in stop. As the tapes progressed towards the middle of the reel, they became less sticky and played or fast motioned over the fixed lifters with no issues. In fact, even the heads and tails of the tape seemed to tolerate fast shuttles over the fixed lifters without sticking or buildup of residue on the lifters themselves.

On some of the reels, a discoloration similar to that shown on the previous sample above was present. Below are more microscope images I grabbed.

Click for higher resolution - Note that the pre bake backing shots were shot at a lower res
(dumbass me - forgot to reset the resolution in the software).
PLEASE NOTE: these samples were clipped from the reel and baked flat on the
flange along with the parent reel, oxide up, about 4" in length.

 PRE BAKE
 POST 4 HOUR BAKE
This is  section 1 which was at the very tail of the tape
This is the next section, which shows less discoloration
This is from about 1 minute into the tape where it was stopped after playing at the playback head

As the tape progressed less debris accumulated to the point that the middle of the tape showed no signs of this and played well.

See Below for
500X photos of this
This is the backing from section 1 as per request from Richard Hess
This is the backing from section 2.


Some 500x closeups of the post-bake "stop" mark - you can download a zip file of the 1280x1024 jpgs here
A Zipfile of two TIFs of the crystal areas can be found here


Here's some shots at 500X of 1990 vintage 1/2" prebake


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