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...
On 1/24/2016 2:05 PM, John Chester wrote:
> On 1/24/16 1:33 PM, John Haley wrote:
>> I have followed this long thread but frankly have found a lot of it
>> confusing. David, I have always assumed it is in fact the black
>> back-coating that is what has turned sticky and gums up the machine on
>> unbaked tapes. It wouldn't be the oxide layer coming off like that.
> In my experience, which is mostly with Ampex tape, both the oxide and
> the backcoating are sticky, and some of the oxide is coming off when
> an unbaked tape is played. The deposit that forms on heads and guides
> exposed to the oxide side of the tape is mostly oxide, although
> initially it seems to be somewhat darker in color than the oxide. I
> think some of the backcoating becomes embedded in the oxide.
> In the worst case, large chunks of oxide are so solidly attached to
> the backcoating that they are pulled off the base. (But I've never
> seen large chunks of backcoating pulled off the base.....)
> The deposit that forms on static surfaces exposed to the back of the
> tape is mostly backcoating.
> -- John Chester
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