Storing photographic materials

Joice Himawan <jhimawan [at] masshist__org> writes

>Our Associate Librarian remembers reading a fairly recent
>publication from NEDCC (technical notes type of thing) that says it
>is okay to use *buffered* tissue for interleaving and folders for
>storing photographs.  Since this is *not* the conventional wisdom
>that I'm familiar with, I'd like to know (a) if this is true?  And
>(b) if anybody can give me the reference info for this publication,
>I'd appreciate it.

The issue of using buffered vs unbuffered paper has a long and
convoluted history which I won't go into here.  Some take the
position that buffered paper is bad for all types of photos, and
others say just to avoid it with cyanotypes, albumen and color
photographs (the advice printed most often in the catalogs).   In
the end, the most crucial elements in preserving one's photos are
the use of enclosures that pass the Photographic Activity Test (ANSI
IT9.16) and maintenance of a stable, appropriate environment.

The ANSI standard IT9.2 Paper Enclosures standard, which was revised
a few years ago updated this information as it pertains to B+W and
Color photographs. The result was to require a minimum alkaline
reserve of 2% molar equivalent of calcium carbonate which gives one
a pH of 8.6-9-5 depending on the buffer used in manufacture. For
paper that is in direct contact with B+W photos (i.e., the
emulsion), the max pH allowed is 9.5 and the minimum is 7.0. For
color photos, buffering is also recommended, but the max pH was set
at 8.0 and a minimum at 7.0. This pH range necessitated an alkaline
reserve less than 2% using the common calcium or magnesium buffers.
The reason for pH8.0 max limit was that yellow stain formation and
cyan dye fading may be increased upon artificial aging after an
emulsion has been immersed in a liquid at pH 8.0 or higher.

To quote the standard "A pH greater than 8.0 may cause increased
yellow stain formation and cyan dye fading, especially under
prolonged adverse environmental conditions of high relative humidity
or immersion in water.  It should be noted that the pH of paper will
decrease with age, especially when used to enclose acidic
photographic materials.  For this reason, an alkaline reserve is
generally recommended for the permanence of the enclosure paper."

My personal view is that a dry envelope in contact with a photo
stored in the recommended environmental conditions is quite
different from immersing a photo in an alkaline solution --albeit a
situation which may be replicated in a flood where long periods of
immersion might occur and if one has newly made buffered envelopes
for enclosures. Under such circumstances, I would be more concerned
about other issues such as mold, delaminating emulsions, absorption
of harmful contaminants dissolved in the water, etc.  Also, I have
never seen  fading, staining or emulsion physical damage that I
could definitively attribute to buffered enclosures.  I have seen
plenty of damage which I could definitively attribute to poor
environmental conditions, poor quality enclosures that don't pass
the PAT (especially lignin containing papers), and poor handling.

Years ago, I tested pH neutral envelopes from a 2 year old package
that had never been opened and found a surface pH of 6; I also
examined envelopes from collections where there were some dates for
when the rehousing had occurred.  I found that buffered envelopes
(labelled pH8.5 at manufacture) that housed acetate films were pH 7
after 10 years and pH 6 after 20 years.

The pH of all papers drops with time, more rapidly if there is no
buffering, or if highly acidic materials are in contact with them.
Therefore, unbuffered papers can be expected to become acidic in
relatively short time (especially if they start out slightly acidic
as I found), and will require replacement sooner than buffered
papers. Replacement will be more frequent if housing highly acidic
materials such as films, poor quality mounts, and poorly processed
photos. This is probably less of an issue in a non-archive type
setting such as a museum where individual fine art photographs are
matted in 4 ply ragboard, at institutions where the collections are
small and replacement is not overly expensive or onerous, or in mat
or album storage where there is a polyester guard sheet on the
emulsion side of the photo.

It's been my experience that in institutions where there are large
staffs/volunteers processing and/or rehousing large diverse research
collections, it can be difficult to maintain separate enclosure
stocks--it seems that people intermix the papers, lose institutional
memory with staff turn over,  or lose commitment to the policy.
Under these circumstances, having one paper stock may seem saner. If
one then chooses only unbuffered enclosures as the single stock,
then one may lose the benefits of an enclosure paper that meets
paper permanence standards and which may provide some benefits to
the paper support of the photograph.

Of course, one may prefer to follow *conventional* wisdom until this
issue is definitively proved one way or another by thorough
research!

Sarah Wagner
Photograph Conservator
Member ANSI Imaging Stability Standards Committees


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                  Conservation DistList Instance 13:43
                Distributed: Wednesday, February 9, 2000
                       Message Id: cdl-13-43-002
                                  ***