[pure-silver] Re: Deteriorating movie film

At 08:40 PM 3/25/2008, you wrote:

DEAR JOHN,
        The first thing I would do is separate the Kodachrome from the B&W.
Then see which one (if not both) is (are) emitting the acidic smell.  There
is the possibility that, if the films had unstable acetate bases they would,
in the presence of moisture and warmth, deteriorate into acetic acid and
other goodies.  I am also worried that what you might be smelling is nitric
acid from nitrate film.  If this is the case you have a very serious fire
hazard on your hands.  To test for this, take a small snip of the b&w film
FAR AWAY from the reels in a fire safe place like over the kitchen sink.
Hold it with tweezers and light it with a match.  If it burns like a very
fast fuse (Pssst!) then you have nitrate and a significant storage challenge
at hand.  If it is acetate it will melt and blacken slowly but not burn
fast.  You will still have a problem if the acetate base is deteriorating
into acetic acid but not a fire hazard.
        I am sure that many who reply will insist that nitrate films went
out in the 30s or, at the latest, 40s but you might be surprised.  I
discovered some nitrate film in some local collections of negatives.  Beyond
the fire concerns nitrate film must be segregated from other film or the
nitric acid will cause image deterioration of the other films.
        In any case it is time to find one of those 16mm scanning services
that will convert your films into DVDs.
                        CHEERS!
                                BOB
I just sent a post on this. Nitrate was _never_ used for 16mm or 8mm motion picture stock. Nitrate was discontinued for all purposes in 1951 but safety stock became available well before this. I think Kodak discontinued the use of nitrate for all still film sometime in the mid 1930's but don't have anything specific. Certainly Ansco made nitrate based sheet film up to 1951. There are two hazards from nitrate film: one is its inflamibility and difficulty of extinguising once ignited. Nitrate film base evolves oxygen when it burns to the flame is self sustaining. Nitrate will burn under water and under sand. The other danger is from decomposing nitrate. The evolved gasses are explosive and toxic. The main danger comes from large amounts of nitrate film stored in small, poorly ventilated enclosures. This is mainly a problem with motion pictures, while the same factors apply to still film it is seldom stored in a manner that allows such concentration of evolved gasses or fuel. There are several symptoms when nitrate decomposes but they are not universal because the mode of decomposition depends on the kind of plasticizers used and other factors. One typical sign is a strong smell of camphor. However, not all nitrate film was made with camphor so it is not a universal symptom. As the nitrate decomposes it also shinks badly becoming cockled and wrinkled. The support can become quite yellow or brown. The surface of reels of motion picture stock become covered with fine, brown, crystals that look like rust. The products of decomposition also attack the image eventually destroying it. There are a couple of tests to determine if film is nitrate but the most reliable one is to burn a small sample. Nitrate burns with a bright flame which can not be extinguished. Acetate film will not sustain flame although it will burn as long as sufficient heat is supplied from an outside source. There is a large literature on cellulose nitrate film base on the web. A google search will find it. 




--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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