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Re: [ARSCLIST] environment controls
As Jerry says, the manufacturers do not release specific information about
the chemical composition and additives in their tapes. Besides the fact
that these components can change frequently, the specific components in each
formulation are the result of expensive R&D which they, understandably, have
no interest in supplying to their competitors.
I don't know of anyone currently doing studies on low-RH effects on tape
components. On the other hand, the general categories of components that
are known are not substances that should be expected to suffer negative
effects at low-RH. Of somewhat more concern has been the effect of
low-temperatures since there have been (undocumented) reports from
manufacturers of lubricant crystallization and/or loss near or below
freezing. ScreenSound, Australia has been doing some preliminary testing on
this possible effect but, so far, has not come up with anything conclusive.
One of the problems, here, is that not all lubricants may be affected. In
addition, where anecdotal evidence of this phenomena has been reported in
the past, it was also reported that warming the tape back up to room
temperature appeared to cause the crystallized lubricant to be re-absorbed
into the binder. This could be seen to imply that, so long as you don't
scrape the crystals off at low temperatures, there would actually be little
or no loss of the lubricant.
As I stated before, the temperature and RH guidelines in the various
standards (AES, ANSI and ISO) are based both on what is known about chemical
decay factors and some purely physical handling factors. The minimum RH
recommendation in these standards is based on tape shrinkage and pack
slippage, not known chemical decay factors.
Peter Brothers
President
SPECS BROS., LLC
(201) 440-6589
www.specsbros.com
Celebrating 20 Years of Restoration and Disaster Recovery Service
> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx]On Behalf Of Jerome Hartke
> Sent: Wednesday, October 29, 2003 12:36 PM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: Re: [ARSCLIST] environment controls
>
>
> Lubricants, as well as other components, can be proprietary. They can be
> either mixed with the magnetic particle-binder slurry (e.g. styrene's or
> fatty-acid esters mixed into polyester-polyurethane or epoxy binders),
> or topically applied synthetic lubricants such as perfluoropolyethers.
> Additional additives are often used to inhibit oxidation and hydrolysis
> of the lubricant.
>
> The resulting matrix, and ongoing process modifications to improve
> performance or reduce cost, do not facilitate meaningful surveys.
> Lubricant evaporation, oxidation, and hydrolysis are the issues, and the
> recommended temperature and humidity conditions are designed to minimize
> these forms of degradation.
>
> Jerry
> Media Sciences, Inc.
> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx]On Behalf Of Jerome Hartke
> Sent: Wednesday, October 29, 2003 12:36 PM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: Re: [ARSCLIST] environment controls
>
>
> Lubricants, as well as other components, can be proprietary. They can be
> either mixed with the magnetic particle-binder slurry (e.g. styrene's or
> fatty-acid esters mixed into polyester-polyurethane or epoxy binders),
> or topically applied synthetic lubricants such as perfluoropolyethers.
> Additional additives are often used to inhibit oxidation and hydrolysis
> of the lubricant.
>
> The resulting matrix, and ongoing process modifications to improve
> performance or reduce cost, do not facilitate meaningful surveys.
> Lubricant evaporation, oxidation, and hydrolysis are the issues, and the
> recommended temperature and humidity conditions are designed to minimize
> these forms of degradation.
>
> Jerry
> Media Sciences, Inc.
>
> Walter Cybulski wrote:
> >
> > Mr. Brothers:
> >
> > Is anyone testing to determine what the effects of low RH
> storage might be on the extended term stability of the
> lubricants, abrasives, &c.? Do the manufacturers release
> information regarding the types and amounts of the ingredients
> used for their tapes? Thanks,
> >
> > Walter Cybulski
> > Preservation & Collection Management Section
> > National Library of Medicine
> >
> > >>> lists@xxxxxxxxxxxxx 10/28/03 12:07PM >>>
> > The ISO recommendation not to go below 15% RH is based on
> contraction of the
> > tape thickness that can lead to loose packs and slippage during
> handling of
> > material removed from low-humidity storage. It is a "shot in
> the dark" RH
> > measurement based on anecdotal evidence and extrapolated
> tension concerns
> > derived from shrinkage formulas from a limited test base. The
> low-end RH
> > limit has nothing to do with decay vectors in magnetic tape.
> There is no
> > known component of polyester-base magnetic tape that requires any water
> > content in the tape at all. The ISO technical commission had no
> > experimental evidence that storage of polyester-base magnetic
> tape at 0% RH
> > would have any negative effect on the tape other than the above
> mentioned
> > possibility of pack slippage. Of course, there may be additives such as
> > lubricant or abrasives that could be effected but have not been
> tested for
> > low-humidity chemical changes. It should be noted that, from a
> > chemistry/decay point of view, no binder hydrolysis at all will occur if
> > polyester-base magnetic tapes are stored at 0% RH- an interesting
> > consideration for long-term storage.
> >
> > Recommendations in the ISO document are a combination of "best
> case" figures
> > modified by practical handling concerns. This means that, within the
> > guidelines given, tape should remain in good condition and
> should be safe to
> > handle. It does not mean that the recommendations given are
> the absolute
> > best for any one specific concern- such as binder hydrolysis decay.
> >
> > Note: the above mentioned opinions are my own as one of the
> primary authors
> > and editors of the ISO storage document and are not intended as
> representing
> > the commission as a whole.
> >
> > Peter Brothers
> > President
> > SPECS BROS., LLC
> > (201) 440-6589
> > www.specsbros.com
> >
> > Celebrating 20 Years of Restoration and Disaster Recovery Service
> >
> > > -----Original Message-----
> > > From: Association for Recorded Sound Discussion List
> > > [mailto:ARSCLIST@xxxxxxx]On Behalf Of Walter Cybulski
> > > Sent: Tuesday, October 28, 2003 9:39 AM
> > > To: ARSCLIST@xxxxxxxxxxxx
> > > Subject: Re: [ARSCLIST] environment controls
> > >
> > >
> > > Thanks for the detailed response, Joe. Lots of people are
> > > looking at that Technical Bulletin. Walter
> > >
> > > >>> Joe_Iraci@xxxxxxxxx 10/28/03 08:40AM >>>
> > > Cooler and drier storage has been cited numerous times for
> extended term
> > > storage conditions of magnetic tapes and other archival
> materials. ISO
> > > 18923 Polyester-base magnetic tape - Storage Practices is one
> source. For
> > > a more thorough discussion on the benefits of lower RH and
> temperature, I
> > > would recommend the CCI Technical Bulletin #23 - Guidelines
> for Humidity
> > > and Temperature for Canadian Archives.
> > >
> > > As for 25% being the "ideal" target, it is not written in
> stone. I guess
> > > 20-30% RH is the ideal range, but because the ISO standard does not
> > > recommend going below 15%, then 25% seems to be the best target
> > > (a bit more
> > > of a buffer to avoid going below 15% because of fluctuations).
> > >
> > > Joe Iraci
> > > Canadian Conservation Institute
>