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ARSCLIST  February 2012

ARSCLIST February 2012

Subject:

Re: Tape Backcoating

From:

Tom Fine <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Wed, 8 Feb 2012 19:22:21 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (233 lines)

Hi Jim:

I should have stated that my comments were limited to audio tape (1.5 mil and 1 mil thickness). I've 
never messed with the thinner tapes and I don't know what the consequences of any of this are with 
non-linear-recorded tapes or information-dense formats.

With what Martin is describing, I can't see why baking does what he is describing it doing. Do you 
or anyone else have some facts as to the mechanism that would cause the globs to remain sticky 
"tar-balls"? All I can think is, they are globs of concentrated goo that can't be baked back to 
non-gooey-ness at a temperature and time that won't damage the playable tape. If it were me with 
those tapes, I would invest a lot of time into seeking backups, even off-air recordings if they are 
radio or TV soundtracks. I think you stand a better chance of getting usable audio that way.

Martin, have you tried freon on those gobs? That's nasty stuff but it worked really well on splices 
that had gone gooey on 1950's brown-oxide tapes that were otherwise fine. The method was, use freon 
to dissolve the splice-goo on the outside of the tape pack, slowly wind to the splice, then very 
conservatively dab freon on whatever small globs of splice-goo were on the tape. If the mylar back 
of the splice had dried out and thus broke the splice, very conservative application of freon was 
used to dissolve all the white dried out glue and sticky goo. Then a new splice was applied 
(cleaning and re-splicing taking place in a splicing block). This worked on 1/4", 1/2" tapes (both 
1.5 mil thick) and 35mm mag-film. I'm wondering if you can rig up something similar to attack those 
globs. I think your problem might be that by the time you expose a glob, it's damaged the playback 
surface (oxide)?

-- Tom Fine

----- Original Message ----- 
From: "Jim Lindner" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, February 08, 2012 6:19 PM
Subject: Re: [ARSCLIST] Tape Backcoating


Tom there are many instances where baking before cleaning is not advised, and Martin nicely 
described just one of them. I would extend that and say that there are many situations where baking 
is not advised at all, and if so only after other processes have been tried beforehand and have 
failed and all other avenues exhausted.

On this list, posters are used to discussion of primarily 1/4" audio tape. There are, however, many 
different types of tape including ones that have completely different binder system from 1/4" audio. 
Some stocks have base films that are just fractions of the thickness of 1/4" audio and have 
recording densities orders of magnitude higher then audio tape. Magnetic Media is used in many 
different application areas and have totally different formulations, thicknesses, and 
characteristics such as abrasivity (for example) are totally different.  Different tapes are 
designed for differing head to tape contact and head tip penetration, and all of these factors are 
critical in the development of appropriate product for the recording format, and they are far from 
the same. Consider the differences between MP and EM tape for example - there is almost nothing the 
same about them other then them being called tape and them having recordings on them. In almost all 
situations baking EM tape would be ill advised.

Some even have the word Video or Data or Instrumentation before the word Tape. These tapes have 
different formulations and respond differently to baking, and even more to the point, SSS is not 
just one thing and has become a general description to a wide variety of maladies that vary a great 
deal in terms of the amount of tenacity of the adhesive as well as the location of it and the 
thickness and composition of it. While a tape may be "sticky", the problem may not be SSS and so the 
appropriate treatment of it may vary considerably.

Not all tapes have linear tracks - and tapes that have helical recordings have some rather different 
issues then those with linear tracks. Deformation in base film of linear recorded tracks - 
particularly if they are wide half or full track audio recordings likely would not be an issue. 
Deformations of basefilm for videotape that have helical recordings and therefore have tracks across 
the tapes (and in particular azimuth recordings on high density recording media), can lead to 
mistracking issues and reduced rf output. This can lead to the loss of servo lock and catastrophic 
failure to play back. This is because non-linear basefilm deformation can cause the tracks to skew. 
Playing back skewed tracks in some formats is extremely difficult - particularly when the skew is 
not consistent from one section of the tape to the next - and the result can be extremely serious. 
Some machines can compensate and other not, and this varies for format type as well as particular 
machine models and even to the specific machine being used for playback and its specific calibration 
at that time. Interchange becomes a huge issue because the deformation of the tracks creates a 
non-standard recording = sometimes - and it may only last a millisecond or two.

Certain tapes have been exposed to damage during their life that would be compounded by baking. 
Tapes that have, for example, particulate contamination or have other types of contamination caused 
by floods or exposure to caustic environments should not just be stuck in the oven because they are 
sticky. I have personally dealt with tapes that have become septically contaminated - and are 
sticky, but there clearly may be other mechanisms in play that can cause the stickiness. Physically 
cleaning tape prophylactically when performed correctly can and has often pre-empted the need for 
baking in virtually thousands of tapes that I personally was involved with over a decade. However, 
there is a certain amount of skill and expertise required.

Taking 2 Asprin and calling the Dr. in the morning may be fine for the common cold but not likely 
helpful for Appendicitis or Cancer.




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 Feb 8, 2012, at 4:48 PM, Tom Fine wrote:

> Who would "advocate" fast-winding or playing a sticky tape before it is baked? That is idiotic 
> advice and should be ignored! The tape is _STUCK_ (ie "sticky") and it will _SHED_ (ie layers of 
> the tape will separate) if the tape pack is molested until it has been baked and cooled. I've 
> never, never had a problem with tapes de-layering after they've been baked the proper time at the 
> proper temperature. I have had tapes (Scotch 227, 3600' reels) that still deposit moderate amounts 
> of white goo on the guides after proper baking and cooling, but they played back fine (there 
> wasn't enough goo to jam up the tape travel).
>
> I can't understand why there is still any "debate" about this -- a sticky-shed tape needs to be 
> baked before anything is done to the tape pack (playback, fast-winding, etc). The good news is, 
> plastic reels can withstand recommended baking temps and times, and if they end up a little 
> warped, just gently/slowly spool the baked tape onto a new reel and dump the warped one. If the 
> tape is on a hub, I recommend you place a flange under the hub, bake it and then handle it very 
> carefully because baking tends to result in a loose tape pack.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Nigel Champion" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, February 08, 2012 3:32 PM
> Subject: Re: [ARSCLIST] Tape Backcoating
>
>
> Perhaps the problem here is not that the tape was baked but that it was re-wound before baking!  I 
> cringe when I see this advocated.
>
> Pressure on inner windings in conjunction with sticky shed syndrome can create a core as solid as 
> a hockey puck, especially if storage conditions have been sub-optimal.  In such situations, 
> pinning and delaminating is almost inevitable.
>
> Good luck
> Nigel
>
> Nigel Champion
> Archive Manager & Audio Conservator
> Archive Of Māori & Pacific Music
> The University of Auckland
> Private Bag 92109
> Auckland 1142
>
> Tel: 64-9-373-7599 ext 85008
> Fax: 64-9-373-7441
> Web: http://www.library.auckland.ac.nz/ampm/
>
> -----Original Message-----
> From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf 
> Of Jim Lindner
> Sent: Wednesday, 8 February 2012 6:41 p.m.
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Tape Backcoating
>
> The backcoat binder system chemistry is in most cases similar if not identical to the oxide binder 
> system, so it sounds like you really do have a mess. Removing one without damaging the other will 
> be extremely difficult. It may be that using a pellon wipe to try to remove it not chemically, but 
> through successive wipes at high speed MIGHT remove enough of it to allow playback, but I would 
> have to see it to tell. It also might be that a low concentration of a solvent will remove the 
> "low hanging fruit" first - so again a pellon wipe with a dilution of solvent and water might 
> work - although you then have the rh issues to deal with, which might also cause problems. These 
> are the "fast and cheap" approaches that might work - but then again you have tried fast and cheap 
> already and have reaped the rewards.
>
> In the past I have used modified film rewinds (with a NAB hub to accommodate tape) and placed the 
> supply reel on one side and the take up reel on the other side - oxide side up in your situation. 
> In between you have your work surface, and you now hand "polish" the tape using a solvent. 
> Unofficially I might suggest experimenting with the now banned 1:1:1 trichloroethane using this 
> modified film rewind approach. Although banned, it may still be available in small quantities from 
> chemistry supply facilities, and yes it is expensive. Fortunately you do not need much. Read the 
> MSDS very carefully, handle very carefully, adequate ventilation, follow all guidelines, hands end 
> eye protection, ventilator - all of it.  This will be a slow hand process. As you get experience 
> you will be able to remove the goo and if you are careful in your application leave the stuff 
> under it. Too much solvent and too much pressure and you will wipe all of it. You "polish" slowly 
> foot by foot winding the completed and clean tape on the take up side. Based on your description 
> you will need to also clean the back coat side because it sounds as if you have softened it enough 
> so that it will reapply itself to the oxide if rewound on it directly based on the pack pressure.
>
> Yeah, well you really do have a mess and a science project. This is just one reason why I am not a 
> big baking fan. There are not too many cases where I see media that is dumpster bound. Next time 
> you might consider cleaning before baking.
>
>
>
> 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 Feb 7, 2012, at 5:18 PM, Martin Fisher wrote:
>
>> Hey Guys,
>>
>> What chemicals are good to strip backcoating off reel tapes.
>>
>> NO!  NO!  NO!  I don't want to send them out for stripping.  Way too expensive.  I don't even 
>> want to strip the entire tape.
>>
>> What I need is to clean the backcoat off the oxide layer.  The tape was given a "B" wind after 
>> developing sticky shed and, in places, some backcoating "hairs" got stuck between adjacent layers 
>> and adhered to the binder.  This was exacerbated further by baking.  The stuff just turned to goo 
>> and spread out on the surface of the binder like butter on bread in the oven.
>>
>> Alcohol works but also dissolves the binder an many instances.  No way of knowing the tape stock 
>> since the boxes are generic, reels are haphazard but the backcoating is of the thick, matte 
>> gooeyer variety.
>>
>> Any help appreciated!  :-)
>>
>> Martin
>>
>

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