3M 996 Shed issue, revisited w/photo

[N7SC]

Several months ago, I had posted a thread about what appeared to be like sticky shed I was having with a box of 996 pancakes that I bought. I had noted that there was mostly white crud and long, thread-like strings. Not the usual brown gunk.

Have been very busy and haven't had time to mess with it since then, until yesterday. Having thought about it for a long time, I thought I'd run a reel through the Revox again to see what happened. Used a reel that had already been through once. Cleaned heads, guides, etc. thoroughly before loading up the tape. Ran it through at 15 ips (to get it over with quickly), and stopped it three times, loosened the tape and checked the heads/guides, etc.

The results: This time through, there was no squealing toward the end of the reel, and there was very, very little build up, if any, until the last 5 minutes of the reel. All the build up was white, filamentous, and there were a few of the thread-like strings that I got the first time that I ran this reel through. I took a photo of the erase head, which was the most affected. See the included photo, the arrows point out the threads and blob of white stuff.

Unless I don't fully understand sticky shed, this doesn't look like sticky shed to me. Do any of you have any ideas what it could be? And, since there appears to have been improvement on the second pass through the machine, do you think it could be cleared up by somehow cleaning the tape?

[Beck]

Sticky-shed will leave behind white or clear glue-like residue. Strings build up along edge-grooves on the head as they are filled in with residue.

Refresh my memory. Was this new, sealed 996?

[N7SC]

Originally Posted by Beck

Sticky-shed will leave behind white or clear glue-like residue. Strings build up along edge-grooves on the head as they are filled in with residue.

You are describing exactly what I am getting. But, does sticky shed diminish with each pass through the machine like this appears to do?

Refresh my memory. Was this new, sealed 996?

Yes, it was a whole box of pancakes, each still in plastic, each still sealed with the 3M adhesive leader on it, never used. The box in question is from pretty early in the production run of 996.

FWIW, it appears that 3M did not actually "seal" pancakes in the plastic bags. Every box of 996 pancakes I've ever gotten has the pancakes in the same type of plastic bags, but the bags are always folded over the same way and kind of tucked in on the pancake trays, but they are not heat sealed shut.

I thought that 996 never suffered from sticky shed.

Maybe, if 996 doesn't normally get sticky shed, then what I'm getting is some mild variant of it. There is no oxide shedding going on, just the white stuff. If this is a milder relative of sticky shed, or something that looks like sticky shed but is not as bad, then do you think baking it might fix it permanently? Or very long term?

[Beck]

See if it comes off with a dry Q-tip... if it does it's not sticky-shed. According to 3M, 996 and 986 (966) are not prone to sticky shed per se. However, these tapes could be showing signs of some other breakdown – maybe just a bad batch. I would expect some light oxide shed, but that should be brown.

3M started using a different binder when 996 and 966 were introduced (so they said). 1991 was before sticky-shed was discovered though, so they didn’t change the binder because of it.

Another idea I’ve seen kicked around in years past is that different brands of tape have slightly different widths. Manufacturers don’t have the same slitting machines to cut the tape. Some 3M tapes, such as 226, were a bit wider than Ampex. Thus, if you have an older machine with a tape path worn by 456, a slightly wider tape will experience edge damage. This could manifest itself with strings of residue, in addition to the normal powdery oxide. Maybe the 1991 batch is a hair wider… or maybe not. I’m not experientially familiar with this, but Steve Albini wrote an article about it 10 years ago or so.

Something to try besides baking, though time consuming, is an alcohol bath. Archivists at the Library of Congress do this for contaminated tape (not sticky-shed).

Use 90% Isopropyl alcohol or better. Run your machine at play speed while holding a lint-free cloth dampened with alcohol against the tape, between the first tape guide and the head assembly. A second piece of cloth should be stretched across the heads to dry the tape and protect the heads. You can cut pieces from an old T-shirt for the cloth. I would fold the cloth that covers the heads so it’s four layers thick.

After the tape has run through, take the full reel and put it back on the supply side. Next, play it through again with the fan blowing on it to facilitate evaporation of any remaining alcohol.

This sort of heroic procedure is normally reserved for recovery of valuable recorded material, but if you really want to keep that tape and have the time it’s worth a try.

Me, unless I had some material I was trying to recover I would cut my losses and start using Quantegy GP9… well actually, on an A77 I would be inclined to use 456 or RMGI 911, but that’s beside the point.