"Environmental law changes forced most tape manufactures to change the formula of their binder in the early 70's."
Read: They used to use whale oil, then they went to synthetic.
As I recall, the sticky Ampex (and of course Shamrock and other bargain brand stuff) existed from about 1968. And it still exists..a few reels of 996 I got about 5 years ago are totally gunked up now. I don't know how 499 will fare.
I still wonder why hardly any 3M 206 was affected.
dl
Charles A. Richardson wrote:Dear Tom: What Claus describes with Ampex sticky tapes is exactly my experience -- they go sticky again after about 30 days. What Claus did not touch on but has definitely been my experience is that there is audible deterioration after two or three bakings. Treble dropoff, fuzzy upper midrange, the kind of stuff you hear in multi-track if it's been run thru too many times for endless punch -ins.
I have spent the last 10 years researching the causes of such tape problems. My own research, as well as the research of a well-regarded forensic chemical laboratory which I engaged to find and explain these complex chemical issues, confirms that the new remediation method that
I devised is very effective and restores the tape to excellent sonic and mechanical performance. Although my research continued and provides more information today, the paper I presented at AES in 2006 in San Francisco provides an explanation and drawings for both these mysteries, namely why the tape becomes sticky again after baking, and why sticky tapes have increasing high frequency losses and drop outs.
If you contact me off list, I would be glad to send you a copy of my paper (and a newer follow-up paper) for your review and comment. In addition I am working on new papers (and a prototype machine to mechanize my process) which will soon be released.
Charles A. Richardson Richardson Magnetic Tape Restoration 1938 Baltimore Annapolis Boulevard Annapolis, MD 21409--6248 410-757-3733
On Apr 2, 2008, at 8:20 PM, Tom Fine wrote:
Hi Goran:
Thanks for digging these posts up.
What Claus describes with Ampex sticky tapes is exactly my experience -- they go sticky again after about 30 days. What Claus did not touch on but has definitely been my experience is that there is audible deterioration after two or three bakings. Treble dropoff, fuzzy upper midrange, the kind of stuff you hear in a multi-track if it's been run thru too many times for endless punch-ins.
I have also had experience with some Ampex tapes so badly stuck together that even baking would not make them un-spool correctly. The oxide would be "glued" to the back-coat of the layer ahead of it and thus would rip the back-coat off and end up an unplayable mess. This was with tapes that had been under extreme storage conditions (basements, attics, garages).
As for 3M, I can say that Scotch 226 and 227 reels I've had the misfortune of dealing with behave pretty much like Ampex tapes. I've never seen this white film discussed in the old posts, just typical sticky-shed that is temporarily cured by baking. However, with 1-mil Scotch 227, I had to bake 18 hours and let cool 18 hours to make one pair of 3600' reels fully playable with no shedding. These particular reels happened to go back sticky within 2 weeks, because I tried to make another go at part of one and ended up with quickly discovering it was sticking and needed another baking. Luckily, the second pass worked great and those reels were disposed of later on.
I have a bunch of Agfa PEM 468 1/2" reels recently given to me. I will report back if I run into any troubles. The two I've played so far are just fine, and one was literally in a basement closet for at least a decade.
-- Tom Fine
----- Original Message ----- From: "Goran Finnberg" <mastering@xxxxxxxxx> To: <ARSCLIST@xxxxxxxxxxxxxxxx> Sent: Wednesday, April 02, 2008 11:11 AM Subject: Re: [ARSCLIST] Fwd: Sticky AGFA PEM 469
Peter Brothers:
The microwave process is called the XT process. It is patented,
That´s correct.
I have saved this from the ARSC list in 2004 that gave some more information coming directly from Terry O´Kelly of BASF:
-----------------------------------------
ctrelby@xxxxxxxxxxxxxxx 9/28/2004 5:06:38 PM >>>
Hi John,
Welcome to the 70's tape pit. I'm sure you have heard about sticky-shed syndrome etc.
Environmental law changes forced most tape manufactures to change the formula of their binder in the early 70's. This has left us with resulting sticky-shed and other artifacts. Scotch/3M I have found not to exhibit sticky-shed unless it was stored VERY poorly, but* A fine white powder will in many cases be released and distribute itself on the tape path and heads. It is very hard to see, and in many cases you have to look at the erase head (it's black) to see this. The powder is fine enough that it will slowly deteriorate the Hi frequency play-back response during a pass. The baking of tapes is not a fix-all solution. It was specifically developed by a group of engineers from Ampex to solve the sticky-shed issues. AGFA developed their own solution to the same problem. (I'll include an email from a BASF engineer to our Video Director at the end of this posting). No such study was done by Scotch/3M to my knowledge but I have found that a pass or two on a pellon based cleaning machine with light tension will clear off the powder and render the tape playable. This process can also be done by hand if you are very careful.
I know this doesn't answer your question about TDK, but I have not encountered tapes from the 70's from TDK, and have no direct solution for you. It sounds like and cleaning pass is in order for you, BUT PROCEED WITH CAUTION, and test on lengths of tape with no audio, since you might damage the tape in trying to find your solution.
The following excerpt is from and email from Terry O'Kelly, formerly of BASF to Pat Shevlin, Xepa Digital. (130 @ 8hrs refers to 10.5" dia, 2" tape - I would still suggest this process is done by engineers with experience to assure a successful result)*
...
"I do have good records of the Agfa XT process and the AMPEX process for driving water molecules out of the polyurethane binder. Agfa used a microwave, but the oven had to be so carefully controlled over a short period of time that it was not generally recommended for users. IDT in West Palm Beach licensed the Afga method, but I don't know if they are still around.
The Ampex method used a convection oven with an internal fan that moved heated air around the tape. The tape was slowly brought to a temperature of 130 degrees F. for a period of about 8 hours. Plastic reels could be used, but it was better to have transferred the tape to a metal reel. The transfer process itself helps to redistribute tension in the tape pack to make it more uniform. More than one tape required a spacer such as an empty metal reel. Once the tapes had cooled to the touch, they were good for about 30 days; but copying the data as soon as possible was safest. The binder would begin to absorb water again after 30 days, but the linking structure of the binder would be damaged enough that a second baking may not have prevented the oxide/binder combination from delaminating or rubbing off altogether.
The goals of both the Ampex and Agfa methods were the same: drive the water molecules out. The XT process was faster but more difficult without a very controlled environment. The Ampex process was slower but easy to follow for most people."
...
I hope you find this helpful.
Claus.
Claus Trelby Managing Engineer/Partner
XEPA Digital 1137 Branchton Road, 19-N-3 Boyers, PA 16020-0137 www.xepadigital.com ctrelby@xxxxxxxxxxxxxxx P:724-794-3686 F:724-794-3292 C:805-490-1730
--------------------------------------------------------------
--Best,
Goran Finnberg The Mastering Room AB Goteborg Sweden
E-mail: mastering@xxxxxxxxx
Learn from the mistakes of others, you can never live long enough to make them all yourself. - John Luther
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