Temporarily curing sticky shed squealing

[Tractorfan]

Hi,
Not sure if this has been done to death before.
I have a recording made in 1979 of a special radio programme about the BBC Radiophonic Workshop. I want to transfer it to minidisc before the sticky shed gets any worse. I can get a reasonable playback by putting it through a graphic equaliser to bring out the top end a bit and reduce the bass.
I was wondering if there's a way to play this tape once more without the squealing caused by sticky shed that seems to modulate the sound, and without having to clean the tape path every couple of minutes? Could I coat the tape with silicone furniture polish such as Mr. Sheen (other polishes are available) to lubricate/seal the tape? I thought about (and tried) running the tape past a felt pad to remove any excess muck which worked to a small degree.I might try dampening said pad with the aforementioned polish & see what happens. I've no idea what kind of tape it is except that it is backcoated, which isn't a problem as I can wedge the pressure pads out of the way.
How do you deal with this problem?
Cheers, Pete

[Paul Stenning]

There is a method of baking tapes which should make it playable for a brief period, allowing you to copy off the contents. Try searching for "baking tapes" and "sticky shed" in these forums. See https://www.vintage-radio.net/forum/...t=baking+tapes as one example.

[Michael Maurice]

I had a problem like this and I reduced the back tension.

Though I was using a Revox A700 and you need to know what to adjust and how to adjust it.

[TIMTAPE]

Baking in a low humidity environment at a suitable temperature and time is the normal procedure. The aim is to remove moisture trapped in the tape binder. The standard advice is to not even play the tape until this preparatory baking is done, as you risk further damaging the tape.
Acetate tapes are different and should not be baked. Baking in a gas fired oven is definitely not advised. Neither is baking in a microwave oven. An electric oven is best.

http://richardhess.com/notes/ has some excellent information on this. Just do a search for tape baking or Sticky Shed Syndrome.

Cheers Tim

Would a couple of weeks in a sealed bag along with a lot of silica gel do the trick?

[TIMTAPE]

I guess it might. I was once advised to place an affected tape in a sealed bag with some dessicant and to place the bag in the roof space of my house, where on sunny days things are warmer, for a couple of days or so. It worked in that case. I guess the heat drove out the moisture and the dessicant soaked it up.

The standard way is a laboratory grade oven with accurate temp control but not everyone has access to that of course.

There's also a vacuum process (low atmosphere to remove moisture) but again not easily available. I haven't tried it myself.

Tim.

[EMI BTR 3]

Originally Posted by Michael Maurice

I had a problem like this and I reduced the back tension.

Though I was using a Revox A700 and you need to know what to adjust and how to adjust it.

One way that sometimes helps, if one has access to a tape machine which can handle 10 1/2" or larger reels and the original tape is on a 5" or 7" reel, is to temporarily respool the tape onto a NAB hub reel, then using this as the supply reel, carefully play the tape with the tape tension selectors set for the smaller reels.

I had a problem like this and I reduced the back tension.

Could the reel be mounted off the deck?

[Tractorfan]

Hi,
I'd clean forgotten about baking them. Silly me . Thanks for the reminder and the links to some very useful info. We too have got a Philips Hostess trolley (didn't they used to be made by Hawkins and then Ekco?) so next time we've got friends over for dinner I can pop the tapes into one of the spare Pyrex glass dishes next to the ones with the rice & carrots.
I'm going to use a Philips N4418 deck which has a motor for rewind/back tension, it's no problem to remove the belt & let the spool freewheel. The pressure pad on the erase head will give the tape a slight braking action.
Cheers, Pete

[Lodgesound]

Use an electric oven - set to 50 degrees - put tape on metal spool and leave in for 30 - 45 mins. Allow to cool down naturally - transfer within a day or 2.

Repeat baking if problem persists.

[geofy]

Baking should be left for cakes, it sounds a bit drastic as a low temp would be hard to control. Why not put it in a car in the sun but out of direct sunlight, gets warm enough in there, take it out in the evening. Not sure which make of car would be best!

[Andrew2]

A couple of my old 70's tapes suffered from this and I couldn't get more than a couple of minutes of decent playback before the squealing and jamming started. As cleaning the heads, guides and tape seemed always to cure it for a wee while, I thought I'd see if I could clean the tape continuously as it passed over the first guide. I fitted a small pad of cotton wool moistened with isopropyl to the guide and allowed this to clean the tape as it was transferring. I got about 20 minutes between cleans and transferred the tape successfully.

[Tractorfan]

Hi & thanks for your thoughts and replies.
I'd been turning various ideas around in my head about how to bake these blessed tapes when I had a light-bulb moment and spotted wifey's slow cooker.
It's perfect! I took out the ceramic cooking pot and tested the temperature. Oh dear, it was just over 230°F, a touch warm methinks. Then spied small variac and tried again at 120volts. Voila! 135°F. There's no thermostat so the temperature will stay constant. That'll do nicely. It fits about 6 seven inch reels and I can also use a plug-in timer to compensate for my lousy memory!
I'll report back and let you know if it works.
Cheers, Pete

[Marconi_MPT4]

Hi,

If anyone is interested, I can post a document provided by Ampex in 1991 regarding this exact problem. At the time, stock of tape used to manufacture data recording equipment was degrading badly even being stored in the correct conditions i.e. temp and humidity controlled. It seems tape manufacture is not a precise art and my findings concluded there are substantial differences even between batches.

Cheers

Rich

[dinkydi]

Hi, In my experience, if you want to get the best results, controlled low-temperature baking is the only way to go. Do not attempt other methods - even attempting playback of a sticky tape will permanently degrade the result of any later remedial action.

The aim of the exercise is to get the sticky emulsion to go back exactly where it came from (back down onto the tape) and if you interfere with the tape surface in any way exact positioning becomes less of a possibility.

Many well known manufacturers made recording tape with this problem in the 60s, 70s, and 80s. The problem occurred because the manufacturers controlled the average polymer length of the emulsion but did not control the distribution of the polymer length. In the problem years the maximum polymer length was relatively long and the average was kept constant with lots of short polymers. The emulsion is hydroscopic and the high density of short polymers meant that the emulsion did not adhere to the tape in the long term.

Peter

[Michael Maurice]

Originally Posted by Marconi_MPT4

Hi,

If anyone is interested, I can post a document provided by Ampex in 1991 regarding this exact problem. At the time, stock of tape used to manufacture data recording equipment was degrading badly even being stored in the correct conditions i.e. temp and humidity controlled. It seems tape manufacture is not a precise art and my findings concluded there are substantial differences even between batches.

Cheers

Rich

Rich, That would be very helpfull, thank you

[Marconi_MPT4]

RE: @MM Rich, That would be very helpfull, thank you

Hi,
Here is the Ampex document. It is a scan of an aging photocopy of a photocopy, making the diagrams a little difficult to see. Hope it is useful.

Still looking for the Jet Propulsion Lab docs... after nearly 20 years they may have long since been recycled.

Cheers

Rich

[dinkydi]

Hi, Twenty years ago I was professionally involved with research on this problem. I have many references in my files that could be scanned/posted here/emailed, if members are interested. Here are some relevant ones:

Ampex "Environmental Aging of Magnetic Tapes" March 1988

D. Anglin "Audio Mastering Archive Stability" Ampex

P. De Lancie "Sticky Shed Syndrome" Mix Magazine, May 1990

B. Jenkinson and G. Welz "On the Problems of Long-Term Storage of Magnetic Video Tapes" Forum News

A. Merkel "When Tapes Start to Feel Their Age" Forum News

R. Muller "On Improvements of Magnetic Tape Shown by Measurements on Early and Newer Tapes" J. Audio Eng. Soc., Vol. 36, No. 10, Oct. 1988

J. Wheeler, "Long-Term Storage of Videotape", SMPTE Journal, June 1983

Some of the references relate to video tape but the problems are the same.

Peter

[Techman]

Originally Posted by Michael Maurice

I had a problem like this and I reduced the back tension.

Though I was using a Revox A700 and you need to know what to adjust and how to adjust it.

Yes, that is exactly what I do.

The way to do it is to rotate the feed reel with your finger so that it's not under any tension....you have to keep that free 'loop' of tape there for the whole length of the tape!

[Paul Stenning]

Originally Posted by Tractorfan

... spotted wifey's slow cooker.
It's perfect! I took out the ceramic cooking pot and tested the temperature. Oh dear, it was just over 230°F, a touch warm methinks. Then spied small variac and tried again at 120volts. Voila! 135°F. There's no thermostat so the temperature will stay constant. That'll do nicely. It fits about 6 seven inch reels and I can also use a plug-in timer to compensate for my lousy memory!

The heating element will be in the bottom so it's probably worth supporting the reel raised up from that so it is heated more evenly.