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ARSCLIST  February 2012

ARSCLIST February 2012

Subject:

Re: Tape Backcoating

From:

"Richard L. Hess" <[log in to unmask]>

Reply-To:

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

Date:

Wed, 8 Feb 2012 20:30:39 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (96 lines)

Martin, for 1/4-inch tapes, I bake routinely 24+ hours in the Nesco at 
54 C (130 C). I don't want to go higher as I've stated previously in 
this thread because of the Tg of the basefilm.

Cheers,

Richard

On 2012-02-08 5:26 PM, Martin Fisher wrote:
> Actually this is not too far from what's happened in my case.  These tapes were played, wound and stopped repeatedly at some point after SSS had set in.  Flakes or hairs of the back coat got stuck between layers in the pack and, over time and pressure, became adhered to both adjacent layers.  Baking only makes the matter worse by turning the particles into goo and allowing them to bleed over the entire width of the tape and sometimes this migrates to spaces between several successive layers.  Repeated winding and stopping has also caused the coating that has collected on the guides and other parts of the transport to dislodge and stick on surfaces where the tape was stopped.  Much of the time this leaves large masses of the coating adhered to the tape.  I suppose it's because the friction of the tape over the buildup has caused the lumps to heat up and fuse with itself.  Again time, pressure and the heat of baking has turned these into large, thin run spots or sometimes massive, hard lumps that easily tear off the oxide binder during unwinding.
>
> I've been baking 1/4 inch tapes for up to 16 hours in a Nesco dehydrator at between 135&  140 degrees in two 8 hour sessions before winding or playing.  (Don't want to leave them running overnight.)  This works fine for most shiny back coated tapes but the matte variety, which easily sheds and is much tackier is a persistent problem.
>
> Thanks Nigel!  :-)
>
> Martin
>
> -----Original Message-----
> From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Nigel Champion
> Sent: Wednesday, February 08, 2012 2:33 PM
> To: [log in to unmask]
> 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 Mori&  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
>>

-- 
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.

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