Hi, John,

I'm sorry, I said "deposition" to cover SSS tapes. Thanks for the 
clarification.

To further clarify, in my worldview--and I am only trying to use this 
taxonomy for the sake of clarification of failure modes and their 
treatment, Soft Binder Syndrome (SBS) is an over-arching condition and 
Sticky Shed Syndrome (SSS) is a subset with, at this point, nothing 
hanging outside the SBS representation in the Venn diagram.

While there may be degrading tapes which are not SBS, SSS tapes so far 
(with or without backcoat) are also SBS tapes. A degrading, non-SBS 
tape, for example, would be an acetate tape which is suffering from 
vinegar syndrome. It is also non-SSS.

To me, the definition of SSS is SBS that can be temporarily reversed 
through "baking" roughly following the rules of the Ampex patent, but 
allowing now for extended baking times.

The treatments that I have been discussing for almost the last decade 
(OY--has it really been that long--it was October 2006, that I presented 
the paper at the AES in San Francisco) such as D5, cold playback, and 
fast playback, are meant for tapes that normally do not respond to 
baking. I see these three methodologies overlapping to some extent 
within the SBS circle, but not overlapping with SSS, by definition.

It may be ultimately shown that those three treatments plus Marie 
O'Connell's isopropynol playback overlap to some extent, if not 
completely. I do not think that any of these four techniques overlap 
with SSS because none of them allow for the separation of the mag coat 
from the back coat when they are adhering firmly enough to pull off the 
mag coat. Those bonds seem to be broken during the baking.

This may be another validation of Peter Brothers' explanation that some 
repolymerization is occurring during the baking. I had always until now 
considered that the bonds between mag coat and back coat are broken 
during the baking cycle.

However, an alternate explanation of the process could be that the mag 
coat's internal bonds (to itself and to the base film on the proper 
side) are strengthened by the baking process to better allow the 
temporary bonds with the back coat to be broken with no ill effect. 
However, if that were the case, I would expect to still hear some 
"ripping" which I do not hear when winding a baked tape.

So that is why I have suggested that the baking process breaks the 
temporary bonds between mag coat and back coat that happen during the 
binder hydrolysis and related failure modes of SSS. I have carried on 
this bond-breaking-by-mechanical-means (thermal contraction and 
expansion) to include cold desiccation's partial success in un-pinning 
pinned, non-back-coated tapes that would suffer from mag coat pullout.

I realize we are putting a very fine point on all of this, but, 
ultimately, I think this increases our (at least my) understanding of 
the mechanism, variants, and cures for tape degradation modalities.

Cheers,

Richard



I realize that a symptom/cure-based taxonomy is less scientific than a 
cause-based taxonomy (binder hydrolysis, vinegar syndrome, etc), but it 
does have a practical application in the field for those of us 
struggling with tapes that are misbehaving. If they ain't misbehavin' 
then they don't get a classification other than, "tape" <smile>.





On 1/25/2016 9:27 PM, John Schroth wrote:
> Hi Richard:
>
> To be clear these tapes I talk about did not have back-coating and
> exhibited classic signs of sticky-shed, They quickly left large binder
> deposits on the heads when tested and responded very well to baking.
>
> These were not squealing tapes, what you have referred to in the past as
> soft binder - that needed cold play or Marie O'Connel's playback method.
> These were sticky shed tapes that did not have back-coating.
>
> My point was that we cannot ALWAYS associate sticky shed with back-coating.
>
> Kind Regards,
>
> John Schroth
> MTS
>
> On 1/24/2016 11:10 PM, Richard L. Hess 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.