Tom:
Just a clarification. There is no binding "glue" material in magnetic tape. The "binder" is the polymers and the "binding" is the chemical bonding between the polymers. Consider the recording surface of the tape like a Jell-o mold with raisons in it (the raisons are the magnetic particles). The jello mold is held together by the jello, not a "glue". Same with the recording and backcoat layers of tape. They are held together by the polymers.
PET is very stable. The only residue confirmed to be from the base layer are the cyclic trimers. These are thought to be left over from the manufacturing process rather than a decay residue as (definition): " In chemistry, a trimer (/ˈtraɪmər/) (tri-, "three" + -mer, "parts") is an oligomer derived from three identical precursors. An example is the procedure of production of polymers. At first, a monomer is made. By combining two monomers, a dimer is produced. With further additions, a trimer and eventually a polymer is made. Often, trimerization competes with polymerization." Note the last sentence of the definition: "Often, trimerization competes with polymerization." This would indicate that the trimers were created when the actual polyester was made and not all of the material was made into polymers.
I consider it a "decay" residue as it doesn't show up on the surface of the tape until other decay issues have become evident and the cyclic trimers migrate through the binder matrix from the base and reach the tape surface.
Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]
Audio and video restoration and re-mastering since 1983
-----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Tom Fine
Sent: Monday, January 25, 2016 8:47 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] One more sticky-shed data point - Richardson treated tape
Am I correct in thinking that tape is made of a base material (polyester, in the case of the sticky tapes we are discussing here), with the recording surface being a mix of metallic flakes and a binding "glue" material? And on the other side of the base, a back-coat of mostly carbon black with a binder material? So this begs a question -- because polyester is a plastic and inherently changes over time, is there any interaction through the polyester between the chemistry of the magnetic surface and the back-coat? Might this have to do with this gooey-ness that doesn't respond to baking, might it be some sort of breakdown of the polyester cause by some sort of chemistry on and through the polyester? Or, in the case of non-back-coated tapes that have this behavior (Sony 150 and maybe the 3M type Richard has mentioned), might there be some sort of chemistry that is turning the polyester itself gooey, and that gooey-ness is "bubbling up" into the magnetic layer?
-- Tom Fine
----- Original Message -----
From: "David Crosthwait" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, January 25, 2016 8:33 PM
Subject: Re: [ARSCLIST] One more sticky-shed data point - Richardson treated tape
Corey,
I've experienced the same with Ampex 147 series 1" type A helical videotape, non-back coated in a
cardboard box. The tape smelled slightly musty, suggesting an above average storage environment. It
was what we call a "pull apart tape". The layers adhered to each other and were very, very dry.
Other Ampex tapes in the collection in similar containers did not have this issue. Only that tape.
On some other formats i.e. 2" Quad, we've seen show recordings that were fine but once we hit the
portion past the recording, there was a near pull apart phenomena. Recently, it was non-back coated
Ampex from 1966.
Best Regards,
David Crosthwait
DC Video
http://www.dcvideo.com/what-we-do/
On Jan 25, 2016, at 3:22 PM, Corey Bailey wrote:
> Hi Peter,
>
> I've run into this a few times. The worst was about 15 years ago with Ampex 456. It was an
> out-take mix of Neil Diamond that had been wound onto a 5" reel with a small hub. Tried everything
> I could think of at the time with no success and that one tape couldn't be saved. It had been
> stored with other tapes (same brand, same age, etc.) that were fine. Some were on individual 7"
> reels (mostly NAB hub diameters), some were on 10.5" reels. Although all of the tapes from that
> lot were sticky and had to be baked, only that one tape exhibited that particular problem to the
> extent that it did. A few of the other tapes shed some oxide on the outer wraps but, fortunately,
> the oxide loss did not affect the modulation. At the time, I suspected that it had been wound
> tight on the reel it was on but had no proof.
>
> Thanks for sharing!
>
> Corey
> Corey Bailey Audio Engineering
> www.baileyzone.net
>
> On 1/25/2016 10:52 AM, lists wrote:
> <SNIP>
>> Here is a weird one that I cannot come up with a scientific answer for:
>>
>> If a tape (backcoated or not- happens to both types) throws a loop or cinches- and the oxide from
>> one wrap is pressed tightly against the oxide from the adjacent wrap in the pack- and remains
>> that way for a while (timing not determined); the oxide layers that are touching each other will
>> occasionally fall off the tape when the tape is unwound. It falls off in a "sheet" across the
>> entire width of the tape and for as far along the tape as the two oxide layers are in contact.
>> This is not an issue of the oxide layer cracking where it is folded over and "peeling" off as the
>> heads hit the crack/crease. We have unwound some of these tapes by hand (very slowly) and the
>> oxide layer just falls off the tape. It is also not an issue of the oxide layers sticking
>> together, overcoming the oxide/base adhesion and ripping off. The "sheets" of oxide are not
>> adhering to the base layer and are not adhering to each other. They appear not to be adhering to
>> anything- they just fall off- very strange.
>>
>> The only thing I can come up with is that the oxide layers and the backcoat have different
>> frictional properties. In addition to all the other ingredients, the oxide layer of many tapes
>> have an abrasive. It is possible that the frictional coefficient of the oxide layers cause them
>> to "lock" together to some degree when they are pressed tightly together inside the pack. If the
>> tape is exposed to temperature changes, the expansion/contraction of the pack, with these two
>> contacting oxide layers "locked together" might, eventually, be enough to loosen the binder
>> adhesion to the base. This is pure speculation but I can't come up with another explanation.
>> Any guesses?
>>
>>
>>
>> Peter Brothers
>> SPECS BROS., LLC
>> 973-777-5055
>> [log in to unmask]
>> Audio and video restoration and re-mastering since 1983
>>
>>
>>
>> -----Original Message-----
>> From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf
>> Of Richard L. Hess
>> Sent: Monday, January 25, 2016 10:52 AM
>> To: [log in to unmask]
>> Subject: Re: [ARSCLIST] One more sticky-shed data point - Richardson treated tape
>>
>> Hi, Shai,
>>
>> The lowering of the Tg is a symptom and has to be caused by something.
>> It is not as if there were a "Tg knob" to turn that down. There has to be a cause.
>>
>> I do not know whether or not hydrolysis is the engine behind the lowering of the Tg. Tg is like
>> body temperature. You might find a way to lower your temperature, but the doctor would like to
>> find the underlying
>> (root) cause.
>>
>> I'm not ruling out Tg drops begin caused by hydrolysis...what other degradation modality might
>> cause this? I will accept that hydrolysis may not always result in sticky shedding.
>>
>> That is why I started to create a symptom- and cure-based taxonomy of failure modes and why I
>> thought "Soft Binder Syndrome" (caused by hydrolysis or not) was a good over-arching category
>> with the Venn diagram circle for traditional sticky-shed syndrome included completely within the
>> SBS circle.
>>
>> Cheers,
>>
>> Richard
>>
>>
>>
>> On 1/25/2016 9:44 AM, Shai Drori wrote:
>>
>>> No, I think Richards theory about the Tg is accurate about cold play.
>>> These tapes do not show any of the signs of SSS but do respond to other methods.
>>> Have I missed anything and someone was able to play them fine after baking?
>>>
>>> Cheers
>>> Shai Drori
>>> Expert digitization services for Audio Video Hi Res scanning for film
>>> 8mm-35mm www.audiovideofilm.com [log in to unmask]
>>>
>>> On Mon, Jan 25, 2016 at 2:45 PM, Tom Fine<[log in to unmask]> wrote:
>>>
>>>
>>>> I'm wondering if this is an extreme case of what I've been
>>>> theorizing about the surface getting degraded from going sticky and then being baked.
>>>> Maybe the Sony and 3M tape that Richard has to cold-play have a
>>>> surface so screwed up, either because it goes very un-smooth or
>>>> something happens where binder material "dries out" so it doesn't
>>>> shed but remains somewhat "rubbery" right at the surface have a
>>>> chemistry that makes hydrolysis particularly damaging to the physics of the material?
>>>>
>>>> -- Tom Fine
>>>>
>>>> ----- Original Message ----- From: "Shai Drori"<[log in to unmask]>
>>>> To:<[log in to unmask]>
>>>> Sent: Monday, January 25, 2016 1:03 AM
>>>> Subject: Re: [ARSCLIST] One more sticky-shed data point - Richardson
>>>> treated tape
>>>>
>>>>
>>>> High Richard
>>>>
>>>>> I think we had a discussion about these two in the past. The PR-150
>>>>> has some batches that run fine but most do squeal. I haven't even
>>>>> tried baking them except once just for the hell of it and of course
>>>>> no luck. Double speed playback works when possible but I haven't had
>>>>> any lately so haven't tried cold play yet.
>>>>>
>>>>> Cheers
>>>>> Shai Drori
>>>>> Expert digitization services for Audio Video Hi Res scanning for
>>>>> film 8mm-35mm www.audiovideofilm.com [log in to unmask]
>>>>>
>>>>> On Mon, Jan 25, 2016 at 6:10 AM, Richard L. Hess<
>>>>> [log in to unmask]>
>>>>> wrote:
>>>>>
>>>>> Hi, John,
>>>>>
>>>>>> This is indeed true. HOWEVER, my success rate for baking tapes that
>>>>>> are suffering from squealing and/or deposition that are not back
>>>>>> coated is much lower.
>>>>>>
>>>>>> This raises another question. If all binder breakdown is
>>>>>> hydrolysis, then why doesn't baking cure it 100%? I'm thinking of Sony PR-150 and 3M-175.
>>>>>>
>>>>>> These two seem to show the falling Tg, but don't have the shedding.
>>>>>> They are outliers and inconsistent.
>>>>>>
>>>>>> Cheers,
>>>>>>
>>>>>> Richard
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 1/24/2016 3:41 PM, John Schroth wrote:
>>>>>>
>>>>>> Back-coating may instigate or speed up the hydrolysis process but I
>>>>>>
>>>>>>> cannot ignore the fact that there are still obscure instances
>>>>>>> where the tape had no back-coating and suffered from SS. Richard,
>>>>>>> you have noted this in the past and I have had this happen in at
>>>>>>> least two instances that I can recall. I'm at home today so I
>>>>>>> don't have access to my notes, but it was clearly sticky shed on
>>>>>>> tapes that had no back-coating. So one should not "always" equate back-coating with sticky
>>>>>>> shed.
>>>>>>>
>>>>>>> Just my two cents...
>>>>>>>
>>>>>>> John Schroth
>>>>>>> MTS
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>>
>>>>>> Richard L. Hess email: [log in to unmask]
>>>>>> Aurora, Ontario, Canada 647 479 2800
>>>>>> http://www.richardhess.com/tape/contact.htm
>>>>>> Quality tape transfers -- even from hard-to-play tapes.
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>
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