Re: [ARSCLIST] Ampex 456

["Peter@xxxxxxxxxxxxx" <lists@xxxxxxxxxxxxx>]

lars:

One thing I noticed, after reviewing the thread generated by your question,
is that no one seems to have asked specifically what you meant in your post
by "really sticky".

What were the symptoms you experienced with the tape?
Were the problems with the signal retrieval or did you have machine
transport problems?
If machine transport problems, how did they manifest?
Did you detect residue on guides or heads?
If you found residue(s), what color and consistency?

At the temperature/RH you describe, you really shouldn't have Binder
hydrolysis problems.  At 8C, you could have problems with contaminants, left
from the manufacturing process, migrating to the surface of the tape.  These
will usually show up as white-ish, yellow-ish, tan-ish or gray-ish powders
or crystals.  These residues can affect frictional coefficients and can
seriously clog playback heads.  Similar to oligomers being re-absorbed into
the binder at higher temperatures, some contaminants are forced out of the
binder at lower temperatures.

At 8C, you also shouldn't really have problems with lubricant
crystallization, but it could be possible.  Some lubricants will crystallize
on the surface of a tape when the tape is exposed to low temperatures for
extended periods (yes it does happen, I have pictures and have dealt with
the problem on numerous occasions).  When this occurs, all that is needed to
get the tape to play back is to leave the tape in a warmer environment for
about 72 hours and the crystals disappear.  We haven't tested to see how
much of the crystallized lubricant is reabsorbed into the binder and how
much, if any, sublimates into the air.  Enough lubricant is reabsorbed,
however, to allow the tape to be played.  If, on the other hand, the
crystals go unnoticed and playback is attempted before re-absorption occurs,
it is possible that the crystals could be scraped off and the tape would
then suffer increased friction due to lubricant loss. (note: not all
observable crystals on a tape surface are lubricant- some crystals are from
other contaminants and do not disappear when exposed to higher temperatures.

Another possibility is, if the tapes were badly hydrolyzed before being put
into the 8C/35%RH environment, the storage conditions could be sufficient to
cause hardening of the oligomer residue on the tape surface.  This could,
conceivably, cause playback problems.  When we have seen this effect,
however, it caused some signal retrieval problems but did not cause
significant machine transport problems.


Peter Brothers
President
SPECS BROS., LLC
(973)777-5055
www.specsbros.com

Restoration and Disaster Recovery Service Since 1983

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx]On Behalf Of Lars Gaustad
> Sent: Friday, June 16, 2006 6:51 AM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: [ARSCLIST] Ampex 456
>
>
> Hi,
> I have got a 2" Apmex 456 that is really sticky.
> I has been stored at 8 C 35% RH for 8 years,
> which makes me believe that the stickyness is not related to hydrolysis
> (SS),
> as such storage should rejuvenate the tape just as well as baking will.
>
> Any suggestions?
>
> lars gaustad
> preservation adviser
> national library of norway
> www.nb.no
>
>