RE: preservation of negatives/slides/prints

[Gawain Weaver <gawain.weaver@gmail.com>]

Hi Richard-- 

1) That's a good question. IPI did find that "paper envelopes offers no
advantage over plastic to control vinegar syndrome" (Environment and
Enclosures in Film Preservation, Bigourdan and Reilly, 1997).

The question here is two-fold. First, does the plastic sleeve prevent the
acidic degradation products from diffusing away from the film? And second,
if it does, does it matter? In other words, does the buildup of acid have
any effect on further degradation?

In theory, since acetate base deterioration has been shown to be
acid-catalyzed and auto-catalytic, the buildup of acidic degradation
products will be harmful. However, in real life practice it is not the
determining factor in the life expectancy of film.


My SPECULATION on it goes something like this: There is no significantly
harmful acid-trapping effect from plastic sleeves on acetate film (di or
tri, they're both unstable) that is still in good condition and does not
have increased acidity levels. At this stage acid production is slow enough
that acid diffusion away from the film is not a significant bottleneck.

Degraded film with high acidity levels will undergo fairly rapid
acid-catalyzed hydrolysis regardless of whether the plastic sleeve prevents
the acid from diffusing away from the film or not. IPI did find that there
was a VERY SMALL advantage to be gained by the use of paper envelopes, but
it is an insignificant factor if one is concerned with long-term
preservation. 

In the end, deteriorating film needs a cold and dry environment, ideally
very cold and moderately dry (say 0F, 25%RH) to essentially arrest
degradation. Short of such cold storage, any cooler storage with moderately
low RH will be a vast improvement over room temperature. Attempts to control
degradation by varying the type of enclosure have proven ineffective.

2) There is no specific risk to scanning, apart from the usual concerns over
care and handling. I was simply warning against the casual use of
digitization for preservation purposes.

3) storage materials to avoid-- just the usual-- PVC, cellulose nitrate or
acetate (that includes Kodak's triacetate sleeves), glassine, and poor
quality paper are generally to be avoided. Of course, the real "acid-test"
in this case is the Photographic Activity Test, and many enclosures have
passed the PAT and are advertised as having done so. As Ryuji noted, untoned
silver gelatin prints are susceptible to damage by many types of inferior
enclosures and other materials like adhesives. Certainly these things should
be taken into account, and good quality enclosures should be used. 

The problem however, is that enclosures are a quick and easy fix, and there
is a tendency to think that once everything is in a good enclosure that the
collection is safe, and this couldn't be farther from the truth. Silver,
nitrate and acetate bases, and color dyes will degrade at room temperature
and moderate RH and or in the presence of common pollutants like sulfur
dioxide, nitrogen oxides, and peroxides. They don't need poor quality
enclosures to degrade. And basements and attics with their extremes of
temperature and humidity will only make matters worse. I trust that Light
Impressions will convince people to use good quality enclosures, but
unfortunately that's not the most important factor by a long shot.

Gawain

-----Original Message-----
From: Richard Knoppow [mailto:dickburk@ix.netcom.com] 
Sent: Tuesday, March 20, 2007 2:33 AM


   Lots of snipping...
    I have a couple of questions. 
1, I generally keep negatives in so called archival envelopes or sleeves, is
there a problem with these when used for acetate film due to the surfaces of
the film being pretty much sealed even though the ends are open?

2, By risk of digitizing for archival purposes do you mean that the archival
storage of the original material may be ignored or is there a specific risk
to scanning?

3, Are there storage materials you would specifically warn against?

   I always read everything you post>



--
Richard Knoppow
dickburk@ix.netcom.com
Los Angeles, CA, USA

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