Photocopying photographs

Just  quick copy of thoughts about electrostatic copier testing with
photos.  NO answers, just problems.  I sent this to Richard directly.

Richard:

The big problem with electro-photographic copying of photographs is that
there really hasn't been any work done it.  I recall one paper done
several years ago.  I haven't found copies of any of them yet, (although
I must admit that I haven't really tried).  The question of
electrostatic copying pops up every so often, but disappears pretty
quickly too (thus why i haven't looked really hard.)  All of the work
was done by Gary Saretzky.

Saretzky, Gary D. (1984). "Research on the Effects of Electrostatic
Copying on Photographs", Conservation Administration News, 19 (October
1984), 21.

Saretzky, Gary D. (1985a). "Additional Research on the Effects of
Electrostatic Copying on Photographs", Conservation Administration News,
23 (October 1985), 8.

Saretzky, Gary D. (1986).  "The Effects of Electrostatic Copying on
Modern Photographs", Book and Paper Group Annual, Volume 4, Washington
DC: American Institute for Conservation, 94-97.

To quote Gary from his paper, "Recent Photographic Conservation and
Preservation Literature", Picturescope, 32 (Winter 1987), 117-132.

    "In response to a caveat by Lewis (1981) that photographs may be
    affected adversely by electrostatic copying.  I exposed test samples
    300 times in copying machines and found minimal, if any effect
    (Saretzky, 1984, 1985a, 1986). Such duplication is often performed
    by archivists and librarians to provide reference copies, primarily
    in order to reduce wear on original prints. Although the fidelity of
    these replicas is usually poor, more sophisticated technology,
    including optical disk (Krayeski, 1984) from which continuous tone
    color images on paper can be produced through electrophoretic
    recording devices (Ehlers, et al., 1983), is beginning to be
    explored."

Much of my concern is that all aspects of the photograph's integrity are
usually not explored due to lack of equipment, time and money. The
copiers have many effects on the photograph including exposure to high
intensity light, possible UV, heat (though briefly) and ozone.  Beyond
the immediate effects on the image one must also explore the effects of
repeat exposure on the physical and chemical properties of the gelatin,
albumen or collodion binder.  The light is known to cause some changes
to gelatin (at least some yellowing.)  How much exposure is required to
cause noticeable yellowing, I don't know.  Some of the yellowing in
albumen is also thought to be due to light exposure--more specifically,
on the effect of light on photo sensitive silver albuminate complexes.
In addition, there are the indirect effects.  How much is the heat
affecting the object?  Is there localized drying that is causing
indirect harm through stress caused by differences in the dimensional
change due to humidity change?  On the other hand, temporary drying may
help increase the resistance of some photographs to the effects of
ozone.  Gelatin, for example, provides a very good barrier against
pollutant gases at low humidity.  Are there synergistic effects caused
by the combination of heat, ozone and light?  Any of these agents may
effect the paper support and perhaps the combination is much worse.
Finally, there may be incipient damage caused by exposure to
electrostatic copiers. One example is from some of the ozone exposure
tests done at IPI on photographic materials.  A reasonably high exposure
in moving air for long periods of time was found to have little of no
effect in one test.  If the exposure was shortened significantly and
then the ozone shut off overnight, complete fading could occur in hours.
Likewise, perhaps the initial period after exposure to ozone, may show
no effect for many hours or days. Finally there are the incipient
photochemical effects.  A compound may absorb light and then react in
numerous ways: thermal equilibrium, internal conversion, radiationless
deactivation, intersystem crossing, fluorescence, phosphorescence,
chemical reaction, sensitization or emission quenching. Chemical
reaction and sensitization are of particular interest since they result
in (or result in potential) chemical change.  Perhaps the kinetics is
such that reaction is a slow step.  Maybe there is a slow sensitization
by a photosensitizing agent.  In the case of sensitizers (such as
mercury vapor or acetophenone, etc.)  one compound absorbs the light
energy and then hands it on to another chemical which may then undergo
one of the prior mentioned actions.  Obviously, the idea of a difference
in kinetics between absorption and reaction of several hours or days is
a little far fetched, but it still makes the point that there may be
latent effects going on that we can't detect for long periods.  We see
the same thing in the degradation of cellulose ester film bases.  For
some reason, if a cellulose ester is subjected to a water trauma such as
flooding in a collection, even if it is dried and subsequently stored
under superb conditions, it still has the tendency of degrading more
rapidly than a similar film support not exposed to water.

In answer to your question about would it be acceptable if 250 exposures
to an electrostatic copier showed no detectable density change in the
image, the answer is not necessarily.  I have not gone into the
deficiencies of densitometers either.  (Densitometers read limited band
widths of the spectrum and therefore tend to be prone to both severe
false negative and false positive results.)  Peter Krause has shown
examples in which obvious (severe) color changes had occurred in a
photograph that were not detected by a densitometer and also images that
showed no visually detectable change that were shown by the densitometer
to have faded to almost nothing.  It is likely that status "A" blue
density readings will pick up reasonably small changes of image tone due
to the conversion of filamentary silver to colloidal silver or
photolytic silver to finer colloidal silver.  However, tinting dyes in
the albumen or collodion may be missed by the densitometer (and blasted
by the light or ozone).

I hope this is of some help even though it does not provide any answers.

-Doug Nishimura
"It has yet to be proven that intelligence has any survival value --
        Arthur C. Clarke"

ps [Maier's Laws:
    1) If facts do not conform to the theory, they must be disposed of.
    2) The bigger the theory, the better.]

One last ps.  [I sent one non-serious ps prior to this one]

Testing by continuous copying (ie telling your machine to make 200
copies) may not reflect real life.  Some reactions, such as light fading
of dyes seem to be governed (in kinetics) by more than just light.  It
is thought that oxygen is required and therefore there is a certain
amount of time needed for diffusion of O2 through the gelatin.  (Thus
high intensity light X low exposure time does not equal lower intensity
X longer exposure time).  Also cycling may be important (especially for
physical stresses).  In real life the photograph would be copied and put
aside, then recopied and put aside.... In addition, long copying
sessions put out a higher concentration of ozone.  In real life, the
photo would absorb some ozone and then "stew" in it for a time and then
absorb some more during the next session and then sit. ...

-Doug

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                  Conservation DistList Instance 4:58
                  Distributed: Saturday, May 11, 1991
                        Message Id: cdl-4-58-002
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