[pure-silver] Re: Deteriorating movie film
- From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Tue, 25 Mar 2008 20:42:32 -0700
At 09:19 PM 3/25/2008, you wrote:
I have just retrieved from storage a large box of 16mm movie film
from the 1950s. Some is Kodachrome taken by my father, and some are
black and white commercial copies from the US of various types of
entertainment, such as cartoons, Charlie Chaplin, travelogues etc.
The box smells strongly of acetic acid, which I understand is the
result of some breakdown of the films. Can anyone tell me if the
two types of film are equally likely to deteriorate, or would there
be a difference between the Kodachrome and the black and white
commercial films? The colour of the Kodachrome looks very good.
John Stockdale
All 16mm movie film ever made was on safety stock. If you do a
google search for "vinegar syndrome" you will find a great deal of
material on line. There were at least three variations of cellulose
acetate stock used, some are more susceptible to decomposition than
others but I don't remember exactly which are which at the moment. My
memory is that the type of stock varied more with time period than
with the kind of emulsion coated on it. As with nitrate stock the
quality varies a lot with manufacturer. Evidently, Dupont stock tends
to decompose more than Kodak.
One artifact of the decomposition of the support is
re-coloration of anti-halation dyes. These dyes are not removed from
the back coating but are de-colorized by the sulfite in the developer
and fixing baths. I am not certain if all motion picture film had
this type of back coating.
A place to start is:
http://aic.stanford.edu/jaic/
But there are many other sources of information.
AFAIK, like decomposition of cellulose nitrate film there is
not much that can be done once the process begins. I would begin with
smelling the film to see if you can determine which reels are the
furthest gone and isolate them from the others. The only way to
preserve the images is to copy them if he support is strong enough to
withstand it. The affected film is likely to also show some physical
signs such as cockling or edge frilling.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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