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ARSCLIST  December 2010

ARSCLIST December 2010

Subject:

Re: SSS and other failure modes (was if you want it done right, do it yourself .../ not always)

From:

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

Reply-To:

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

Date:

Wed, 22 Dec 2010 17:39:15 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (113 lines)

Hi, Shai and Michael (and Michael from off-list),

I am here wrapping Christmas presents for my family...and figuring how 
to deal with 17 microphones (9 wireless) for the church Christmas 
Pageant Friday afternoon at the 3 and 5 PM services.

Anyway, this is a complex issue and is addressed to some degree in my 
paper from the ARSC Journal.

My paper on tape degradation that was originally presented at the Audio 
Engineering Society's 121st convention in October 2006 in San Francisco 
was published in the ARSC Journal in the Fall of 2008. It is available here:
http://www.richardhess.com/tape/history/HESS_Tape_Degradation_ARSC_Journal_39-2.pdf

However, this discussion is equating SSS with back coating.

What I think I know is:

(a) Almost all SSS tapes also have back coating.
(b) Not all back-coated tapes exhibit SSS.
(c) Charlie Richardson claims that removing the back coating will 
restore the tapes. He can discuss his findings in greater detail. I 
can't speak for him or his patented process which I have never tried to 
replicate.
(d) The chemistries of the mag coat and the back coat may be similar or 
different, depending on the tape.
(e) The precise chemical makeup of the tapes is unknowable at this point.
(f) The degradation trajectory relating to basic chemistry, 
out-of-control processes (i.e. out of spec tape) and storage conditions 
is impossible to know at this point.
(g) It appears that at least some manufacturers of some tape types 
substantially changed the tape chemistries while maintaining the same 
"model number". This is best documented by Benoit Thiebaut in his 
testing of video cassettes for Presto Space.
(h) We think that polyester polyurethane binders were introduced about 
the same time back coating was introduced, so there may be no 
cause-and-effect relationship.
(i) Some archives (I believe Screensound Australia) interleaves paper 
leader with back-coated tapes so that the back coat and mag coat are not 
in direct contact.
(j) While the analogy may fail, have you ever seen an electrostatic copy 
(like a Xerox) that has spent a long time in direct contact with a vinyl 
binder? It's enough to make one wonder, at least.
(k) Some polyester-polyurethane compounds do a good job of breaking down 
when exposed to moisture, especially at elevated temperatures.
(l) Bradshaw did enough work to disprove that the chains re-link when 
baking as it just doesn't happen in a filled matrix.

So, that's off the top of my head in five minutes...there is no simple 
answer and I doubt we'll ever have something as easy to use as a "pool 
test kit" for determining the likelihood of future SSS failure. If it 
says Ampex 406/407/456 on the box/reel and there is no reason to 
disbelieve it, bake before winding.

I was also asked off-list about the composition of the back coat and I 
suggest the answer is really (e), above. Yes, carbon black is in many of 
the back coats to drain off static, but the "bad actor" here is not the 
carbon black but rather the binder chemistry. Also, I've never seen a 
back-coated audio CASSETTE tape. Has anyone?

I have some SM911 that is going bad--I'm not certain it's SSS or just 
shedding. I forget if it's BASF or EMTEC.

Here is a list of degrading tapes that I _attempt_ to keep current.
http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/degrading-tapes/

I've been asked to do work on some Sony PR-150--pray for me.

Cheers,

Richard

On 2010-12-22 2:13 PM, Shai Drori wrote:
> It's a good argument, but has it been tested. Has anyone tried to 
> store a back coated tape without it's back coating to see the 
> difference? If I remember correctly (where is Rich Hess when you need 
> him) the SSS was first discovered in ampex 400 series, but it was the 
> new binder they used. I don't see how that is affected by the back 
> coating, and why doesn't it affect all back coated tapes. I have many 
> different tapes with back coating, some of them almost 30 years old by 
> now that play like the day I bought them. Maxell XLI, BASF pem468,  
> BASF dpr26, emtec 911 (not 30 years old). To put the blame on the back 
> coating just because if is from the same era. It should have sown up 
> in all back coated tapes. What am I missing?
> Shai
>
> On 12/22/2010 8:47 PM, Michael Biel wrote:
>> On 12/22/2010 2:27 AM, Shai Drori wrote:
>>> I have many tape that are back coated that show no SSS. In my 
>>> experience there is no connection whatsoever.
>>> Shai
>>>
>>
>> But how often have you found non-backcoated tapes with SSS?
>>
>> Mike Biel  [log in to unmask]
>>
>>
>>> On 12/22/2010 8:46 AM, Michael Biel wrote:
>>>> The one saving grace of 8mm is that I don't think I have come 
>>>> across a backcoated tape in this format.  So if there is any truth 
>>>> to SSS being a reaction to backcoating, that reduces that problem.
>>>>
>>>> Mike Biel  [log in to unmask]
>>
>

-- 
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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