Nitrate

Some more thoughts on nitrate film:

The storage of nitrate film under improper storage conditions can very
much constitute a high health and safety risk.  I must temper the old
concerns about nitrate film deterioration however, with newer
information.  In a recent study by the Image Permanence Institute, we
incubated nitrate, 2 brands of cellulose triacetate, cellulose
diacetate, cellulose acetate propionate, an old and new cellulose
acetate butyrate films and polyester.  Although the hydrolysis
deterioration process is auto-catalytic and therefore, by no means a
first order rate reaction, it is possible to select end points for the
various tests and produce a pseudo-first order reaction curve.  This
method has been used for a few years by ANSI and the photographic
manufacturers to predict the life expectancies of color materials (dark
fading) and film bases.  The data shows that all of the cellulosic
esters at 50% RH and 20 deg. C will last about the same length of time.
The data may be a bit skewed due to film availablility, but is offset by
age.  The acetate propionate, diacetate and nitrate films have not been
manufactured in 40 to 60 years.  The fact that we had nitrate film in
good shape, showed that it had to have been one of the more stable
nitrates.  Therefore, as a representative sample, this film may produce
high predicted life expectancies for nitrate.  On the other hand, the
film already was at least 40 years old when it entered the incubations
and therefore, the figures obtained should really have another 40 years
added on (for the real life aging).  The nitrate film showed to be very
humidity dependent on it's aging rate.  Keeping the film at a drier 20%
RH would improve the life expectancy of the film by possibly as much as
10 times.

Nitrate film from an archive point of view, is not as bad as it once was
thought.  Copying programs should deal with whatever film type needs it
(be it triacetate or nitrate).  However, from a safety point of view, if
a collection is not prepared to handle the possible safety problems, the
film should be copied and either stored off site or destroyed.

In a test performed at Fort Lee, NJ in 1915, 1900 pounds of nitrate was
placed in a vault with NFPA approved ventilation, but no sprinkler
system.  The film was ignited.  A tongue of flame 8 feet in diameter and
70 feet long blasted out of the vent outside and lasted for 90 seconds.
I was most impressed when I read about the test (little boys are
fascinated with things that burn).   I tried to convince the director
here, James Reilly, that we should re-do the test (after all it was done
75 years ago), but he didn't think that RIT would approve.  :^)

BTW if anyone is getting rid of old nitrate in good condition, the Image
Permanence Institute is looking for rolls at least a thousand feet long.
We need large amount of film from the same batch and stored in the same
way.  The film used for the previous study was Dmin processed film from
the Humanities Research Center in Austin, Texas.

                           -Douglas Nishimura

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                  Conservation DistList Instance 4:10
                  Distributed: Friday, August 17, 1990
                        Message Id: cdl-4-10-001
                                  ***