JFARRINGTON@EAGLE.WESLEYAN.EDU (Jim Farrington) (10/10/90)
In reply to Steve Graham's squealing reels, I think I can throw some light on the subject (though you may not like the answer). Until the '70s one of the main components to audio tape was whale oil as it was and is the best agent for keeping tape supple. When whaling began to be frowned upon, companies began to look for new agents to replace the whale oil. As we are hearing now, the stuff they began using in the '70s is now disappearing from the tape which is becoming brittle and "sticky". The high-pitched squeal you hear is actually the tape catching and releasing on the heads many thousands of times per second. Ampex tapes from this time are notoriously bad in this respect. Last Formula 9 helps on the heads to reduce friction, but is not the whole answer. What you need to do is go to a fabric store and buy some stuff called "Pellon", a non-woven material used as a backing when making clothes. Cut it up to make little patches you can hold between forefinger and thumb. The hard part, at least time-consuming-wise, is to sit there and run the tape through fast forward (not in contact with the heads) while pinching the tape between the covers of the pellon-patch. Depending on the severity of the problem this may need to be done more than once. This is the only known way to render the tape playable so as to get one more pass over the heads and re-recorded. Jim Farrington Music Librarian Wesleyan University JFARRINGTON@WESLEYAN.BITNET jfarrington@eagle.wesleyan.edu ALANET: MLA.NEWS.ED "A librarian ought not to content himself with giving the public what it happens to want, but ought to help create a demand for what the public needs...." Oscar Sonneck, 1917.
cbp@foster.avid.oz.au (Cameron Paine) (10/16/90)
In <6869@uwm.edu> JFARRINGTON@EAGLE.WESLEYAN.EDU (Jim Farrington) writes: >In reply to Steve Graham's squealing reels, I think I can throw some light >on the subject (though you may not like the answer). [...] Following this topic has made me feel slightly ill... We have ~500 hours of seminal local music which was recorded onto (predominantly) Ampex tape between 1979 and 1985. I have banned playing these tapes until I find a way of extracting the material and this thread has provided the first concrete information I've encountered. I had developed a different theory and I'll mention it briefly because I think it has some merit. Note, I'm not arguing the point with Jim. Tape relies on air as a lubricant. A layer of air molecules is trapped between the successive layers of tape as it is packed onto the take-up spool. The trapped air reduces the adhesion between adjacent tape layers. I offer three observations to support this theory: * the shape of the `cutouts' on tape spools can noticeably effect the tape packing density. I believe this is because there is a relationship between airflow over the tape and the size (and possibly the shape) of the cutouts. * tape that has been stored and not played for a long period of time produces the scrape-flutter effect; tape of a similar age that is used more frequently is less likely to exhibit the problem. I ascribe this to a gradual loss of the air layer over time. * I have successfully eliminated the scrape-flutter effect by repacking the tape. This is a very tedious process since the best effects are achieved by multiple (> 10) unspool/respool cycles. I have used both a tape machine and a cart-winding machine to achieve this. >Last Formula 9 helps on the heads to reduce friction, but is not the whole >answer. What you need to do is go to a fabric store and buy some stuff called >"Pellon", a non-woven material used as a backing when making clothes. [...] I fear that `Pellon' is a trade name, which is why I am having difficulty locating it. Do you have any idea of its composition? Alternatively, do you know who makes it? I assume that you've attempted this process yourself. What effect does the friction caused by the Pellon have on the oxide layer. Some of our tapes are from BASF and these are notorious for shedding their oxide. Have you noticed any disturbance in the dimensional stability of the base material? Any other nasty side effects? For those who are interested, I've posted a related article that explores the next step - a better archiving medium. Cameron (aka O.B. Coordinator, Radio 3PBS-FM, Melbourne, Australia) -- cbp@foster.avid.oz - ACSnet cbp@foster.avid.oz.au - Internet ...!{hplabs,mcvax,nttlab,ukc,uunet}!munnari!foster.avid.oz.au!cbp - UUCP
urban@frith.egr.msu.edu (Mark Urban-Lurain) (10/17/90)
In article <6869@uwm.edu> JFARRINGTON@EAGLE.WESLEYAN.EDU (Jim Farrington) writes: >In reply to Steve Graham's squealing reels, I think I can throw some light >on the subject (though you may not like the answer). Until the '70s one >of the main components to audio tape was whale oil as it was and is the best >agent for keeping tape supple. When whaling began to be frowned upon, companies >began to look for new agents to replace the whale oil. As we are hearing >now, the stuff they began using in the '70s is now disappearing from the >tape which is becoming brittle and "sticky". The high-pitched squeal you hear >is actually the tape catching and releasing on the heads many thousands of >times per second. Ampex tapes from this time are notoriously bad in this >respect. One article (sorry ,don't have the reference handy) I recently read said that the problem was not that these lubricants evaporate, but that they actually undergo chemical changes which cause them to become "sticky". The solution they proposed was to fastwind the tape a couple of times, then bake it in a low (~200 degree f) oven to dry out the lubricant. They then suggest playing only for dubbing purposes, as the tape will have no lubricant, but at least would not have an "adhesive". I've not tried it as it seems a little radical; I think I'd try the cloth method Jim proposes first. -- Mark Urban-Lurain urban@cpswh.cps.msu.edu Computer Science Dept. urbanluraimg@clvax1.cl.msu.edu Michigan State University (517) 353-0682 A-714 Wells Hall, East Lansing, MI 48824
bill@uunet.UU.NET (Bill Vermillion) (10/18/90)
In article <6998@uwm.edu> cbp@foster.avid.oz.au (Cameron Paine) writes: >In <6869@uwm.edu> JFARRINGTON@EAGLE.WESLEYAN.EDU (Jim Farrington) writes: > >>In reply to Steve Graham's squealing reels, I think I can throw some light >>on the subject (though you may not like the answer). [...] > >Following this topic has made me feel slightly ill... We have ~500 hours >of seminal local music which was recorded onto (predominantly) Ampex tape >between 1979 and 1985. I have banned playing these tapes until I find a >way of extracting the material and this thread has provided the first >concrete information I've encountered. I had developed a different theory >and I'll mention it briefly because I think it has some merit. Note, I'm >not arguing the point with Jim. > Tape doesn't rely on air as a lubricant. The lubricant is built into the oxide. There have been major problems in the last few years with oxide formulations as suppliers to the manufacturers sometimes change chemical composition of certain supplies, which affect other things along the way. We had a problem with this with a bunch of Ampex tape (2" Grand Master) several years ago, and the oxide would become gummy. Another problem surfaced on Scotch whereby the carbon impregenated backing would adhere to the oxide and would then be stuck to the heads. Sometimes the would occur within a minute of playing. A friend of mine lost the master mixes of the "Blackfoot Live" recorded in London. When the tape was finished playing enough of the oxide had come off that the tape was junked. The only good part of this was the failure occured during the transfer to PCM digital, so the mix is still available. This has become a major problem. So much so that Agfa has researched it thoroughly and has developed a process to re-lubricate the tape enough so that a transfer can be made onto better media. I understand it involves coating the tape and baking it. It is a laboratory procedure, and I understand they do it in LA, but not sure if done anywhere else. That would be the last resort but it won't be cheap. I have seen tape disintegrate in various way. I have seen oxide flake off the tape. This occurs when the oxide and the backing material and the oxide shrink or dry out at differing rates. More typical with acetate than mylar based media. Splices are another killer. No one seems to have perfected a splicing tape that works right. I have had some that bleed in a matter of months. Others that completely dry out. You mention that repacking the tape about 10 times or more helps. But I suspect it is not the air, but moisture from the air helping to relubricate the tape. You don't want air between the tape and the head, you want intimate contact. I have had moderate success with holding the tape between the folds of a record cleaning cloth. But I don't know if they make those anymore. These were the cleaning cloths with silicone impregnated in them. Best of luck. You will need it. bill -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP