Print

Print


Greg:

Tape delamination is a very difficult problem to deal with but a number of
possible solutions have been tried (with varied success).

Delamination can be associated with binder hydrolysis but may also be caused
by other issues.  Under certain circumstances, hydrolysis residue on the
surface of a tape can cause sufficient inter-wrap adhesion to cause the
layers to delaminate.  

Another possible cause, however, is repeated exposure to wide variations in
temperature and humidity where the slight difference in the expansion and
contraction of the layers might cause delamination.  Since the primary
vector of expansion and contraction in polyester-base magnetic tape is
thickness, wide temperature/humidity variations will cause the tape pack to
tighten and loosen.  This repeated tension and loosening of the tape could
easily cause delamination.

If your tapes appear to be delaminating, it is important to get them into a
stable environment.  As to how you might treat them, this is dependent on
the delamination mechanism.  Are the tapes delaminating due to adhesion
between tape wraps or are they delaminating without inter-wrap adhesion.  If
the cause is adhesion, incubation or baking could help.  If there is no
inter-wrap adhesion, you have a more difficult problem.

If the chemical bonds between the various layers of the tape have "failed",
regular baking techniques (in our testing) have not been effective and, in
some circumstances, have aggravated the problem.  Rather than "baking", cold
desiccation has sometimes proven effective.  To do this requires you isolate
the tapes in a fairly cold and stable environment (refrigerate, do not
freeze).  The environment must also have a very low humidity (30% RH or
less).  Delaminated 2" tapes left in this environment over a period of 3 to
6 months have shown partial re-attachment of the layers that had previously
delaminated.  The re-attachment has been sufficient that about 60+% of the
tapes tested were able to be played.  The process does not always work.

The reason and mechanism behind the "re-lamination" is a little too complex
to get into here but we have used this process on over a hundred 2" tapes
with around a 70% success- obviously not perfect, but a lot better than
having flakes (or even sheets) of recording layer fall off the tape during
playback.

We have another method we have used that has had a 100% success rate but we
only used it on two tapes so the sample is too small to be meaningful.  This
procedure is extreme and I would rather not put in print and potentially end
up with an on-line argument.  If you want to contact me directly, I would be
willing to discuss both procedures.

Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]

Tape restoration, disaster recovery and re-mastering since 1983   

 

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Greg Schmitz
Sent: Thursday, July 18, 2013 4:57 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] Conservation question: oxide delamination and
consolidation

The Soundscriber SS-124 was advertised by Soundscriber as using a Mylar 
based tape - hence polyester. Thank you to all that have replied to my 
inquiry. I am familiar with the common issues related to magnetic tape 
stock - SS, VS, and so forth. The climate here in Alaska is, in the 
main, actually favorable to the long term storage of film and magnetic 
mediums. 9 times out of 10 I can tell when media has been stored out of 
state because in most cases it has deteriorated much faster than it 
would have if it had spent its "life" in Alaska. So I would ask again 
about the consolidation of delaminataed coatings on a polyester base and 
what techniques might be helpful. References to papers or commentaries 
on the subject would be greatly appreciated by me, and I suspect by many 
others.

Thanks again. --greg

On 7/16/13 9:03 PM, Jim Lindner wrote:
> In the original question Greg said that these were 2" Helically recorded
tapes from the 1960's on a SoundScriber  - typically these types of
recordings were used for air checks or dictation/transcriptions or  logging
phone calls over very long time periods.  I am pretty sure that the base
stock would be Polyester and not Acetate.
>
> That said, I would agree that baking is likely not advisable if
delimitation is occurring (or even if it isn't with something as finicky as
this), at least without a great deal of inspection and work first to try to
figure out precisely what is going on and to develop a treatment plan for
the specific problem.
>
> Consider - this is polyester that has helical tracks (long ones on 2"
tape) moving VERY slowly for recording, that has been stored in
non-temperature controlled environment in Alaska for about 40 - 50 years.
You can imagine what the material has done over time - now track that with a
period device - forget AST or any fancy technology to make sure that the
head is where the track happens to be based on the distortion that has
occurred. Yikes!
>
> I would definitely not bake these tapes until I tried a whole bunch of
other things first.
>
>
>
> Jim Lindner
>
> Email: [log in to unmask]
>
>    Media Matters LLC.
>    450 West 31st Street 4th Floor
>    New York, N.Y. 10001
>
> eFax (646) 349-4475
> Mobile: (917) 945-2662
>
> www.media-matters.net
> Media Matters LLC. is a technical consultancy specializing in archival
audio and video material. We provide advice and analysis, to media archives
that apply the beneficial advances in technology to collection management.
>
>
>
>
>
> On Jul 16, 2013, at 7:54 PM, Tom Fine<[log in to unmask]>  wrote:
>
>> Totally agree with Matt on this one. The WORST thing you can do to
acetate is make it hotter and drier.
>>
>> -- Tom Fine
>>
>> ----- Original Message ----- From: "Matthew
Sohn"<[log in to unmask]>
>> To:<[log in to unmask]>
>> Sent: Tuesday, July 16, 2013 6:29 PM
>> Subject: Re: [ARSCLIST] Conservation question: oxide delamination and
consolidation
>>
>>
>>>> Whoa - wait a minute.
>>>> Isn't binder hydrolysis (sticky shed) totally different than binder
delamination? Would you really want to bake tapes with
oxide>delamination???? Some tapes may have sticky shed so bad that it
appears to be "delaminating" as you play them, but I'm not so sure
that>you'd want to bake tapes where the binder is actually flaking off of
the tapes just by handling them. I have not yet had to work with true>binder
delamination (and hope I never will) but from what I know, that's a totally
different animal not to be to confused with sticky>shed!!! (and I've yet to
see anyone out there reveal any simple solution to easily fix or stabilize
binder delaminated tapes). Just my two>cents. Suzanne if you have more
information, please share it!
>>>> John Schroth
>>> The only binder delamination I have encountered have been on very old
acetate-backed tapes. It seems to me that it is a lack-of-humidity problem
that may or may not be remedied by placing the tape(s) in a high humidity
chamber for a long period of time (think weeks or months) before attempting
to play. I would never bake an acetate-based tape.
>>>
>>> -Matt Sohn
>>>


-- 
Greg Schmitz
Alaska Moving Image Preservation Association (AMIPA)
Anchorage, Alaska
greg /at/ amipa.org

The Alaska Moving Image Preservation Association is a 501(c)(3) non-profit
dedicated to media preservation and education to ensure long-term access to
Alaska's moving image heritage.