Parker Dinkins wrote:I think contact with a smoother surface might cause this, and not necessarily because it's another record-layer. I've seen the record-layer binder come completely off on the smooth hub of the reel, and especially on early 3M plastic leader tape, which is relatively shiny and smooth. Then when the wrap is against the back-coat, everything stays in place.
I have had this problem as well, only once with the hub, but more often with the 3M plastic leader. I asked about how to deal with it during the "Ask the Technical Comittee" session at the last ARSC conference, and the only answer I got was to "unwind the tape very carefully". In my experience, the leader tape problem seems to occur with 3M plastic leader used between late 1977 and early 1978, and seems to be confined to Ampex 406-407 and 456-457. In the current project I am working on I see it on virtually every one of the tapes from that period from those tape stocks. Tapes from early 1976 and late 1978 are not affected, and in the few cases where yellow leader is used on 1977 tapes, the problem does not occur. There are a few reels of Maxell tape from the same time period that don't have the same problem (and don't require baking either). Since these tapes are sticky-shed and stored tails-out, I was baking them before rewinding, and when rewinding, the wrap where the oxide contacted the leader would lose chunks of oxide (blocking, I belive it is called), which was adhered to the leader. Once I realized that it was not a one-time occurence, I would rewind until just before the leader, stop the machine, and very carefully peel the final wrap off the leader, but I still got oxide coming off on the leader (not blocking, but traces). Some of the tapes had leader between every song, and I noticed that it got worse as I got closer to the hub. The layers nearer to the outside would unwind fine, but the closer to the hub, the worse it got (tension-related?). The problem seems to be exacerbated by baking. A few tapes that were stored heads-out did not exhibit any problems, but the wraps of leader would be sticking to themselves as they unwound.
I tried an experiment, where I rewound a reel (bypassing the tape path) before baking it, and had no problems playing it. The oxide did not adhere to the leader when rewinding, but after baking, the wraps of leader were sticking to each other. Since then, I have chosen the lesser of two evils and rewind tapes (bypassing the tape path) before baking when I have leader present. I suspect a bad batch of leader, combined with SSS.
One other thing. For the tapes with chunks of oxide stuck to the leader, I was able to minmize the dropouts by the following process:
I cut the tape from the leader, flip it over and re-splice it at both ends, then record the tape. Then, using the Audio Montage in Wavelab, I copy and paste the affected portion of the track into one stereo track of the montage. Then I copy the portion of the leader containing audio signal, open it up in it's own window (as a new audio file), reverse the channels and phase-invert them. then I place that audio into another stereo track in the Montage, very carefully line up the waveforms on the timeline, and render a new file from that. Then I render the Montage as a new audio file and paste it back into the original file, replacing the affected portion of audio. It's time-consuming and a pain in the tucchus, but I have gotten very good results using this method, and the more cleany the oxide has adhered to the leader, the better the results have been. Unfortunately this method won't work when the oxide is stuck to the hub..
-Matt Sohn