Nitrate base, the pioneer of motion picture film bases, retired
 from our cameras and laboratories about 1951-52. Still, its
 very long shadow of distinguished commercial motion pictures
 and film records haunts many film vaults. Nitrate base films
 must be handled with informed care.


 Cellulose nitrate base film is relatively unstable. If you
 store it in large quantities of about 5,000 feet or more and in
 non approved storage cabinets without proper ventilation, it
 becomes a fire hazard. Admittedly, it takes a bit of pushing to
 cause it to burst into flames spontaneously. For example, in
 one laboratory test, combustion occurred with a decomposing
 1,000 foot roll of film only after it was kept at 41°C (106°F)
 for 17 days tightly encased in a can wrapped in insulation to
 retain the heat of decomposition. However, even a minor fire
 can cause major film losses. This example may not be that
 different from some storage lofts in the summertime that are
 uninsulated.


 Cellulose nitrate decomposition is the villain. It shrinks,
 even to the point of becoming unusable. Furthermore, as the
 film breaks down, it gives off nitric oxide, nitrogen dioxide,
 and other gases that yellow the film base, yellow and soften
 gelatin, and oxidize the silver image. Later, the base cockles,
 becoming very brittle and then sticky. Finally, it
 disintegrates completely. This inevitable deterioration is
 usually gradual, but elevated temperatures and humidity speed
 it greatly.


 While it deteriorates, nitrate base film makes a kind of
 pressure cooker of the film can in which it rests, especially
 when it's taped closed. If the gases can't escape, heat builds
 and spontaneous combustion may not be far behind. Therefore,
 nitrate film must never be closed in.


 Escaping toxic gases (powerful oxidizing agents) can attack
 nearby acetate and polyester base films, so store nitrate films
 in their own special place and not in a place too heavily
 concentrated.


 If the conditions are right, their image layers may last for
 decades or generations. Because of their great value, many
 nitrate base films have been reprinted on current longer
 lasting safety base. Somewhere, nitrate film is still with us,
 so we offer a few more comments.


 Probability of Rapid Decomposition
 If you store old nitrate base films, the first thing you need
 to check is the temperature of the storage area. High readings
 of the temperature and/or the relative humidity are unfavorable
 to nitrate and to other films. Are the by products of
 decomposition being discharged from the storage area? Is there
 too much nitrate in a confined area? The more rolls collected
 in one place, the greater the chance of trouble. with nitrate
 film, it's important to design separate and specialized storage
 compartments.


 Inspection and Segregation of Nitrate Base Film
 Identification is the key to initiating the proper handling of
 nitrate film. You need to properly identify the films in your
 vaults and storage areas. Don't assume all films to be acetate
 or polyester when some may be nitrate. Some rolls may be
 spliced mixtures of each. Kodak never produced 16 mm or
 narrower film on nitrate base. Some may have been slit to 16 mm
 from 35 mm for whatever reason. Also, Kodak never produced 70
 mm or 35 mm color camera original or color print films on
 nitrate base, but they did produce on nitrate base a special
 black and white Eastman nitrate film for use in making 35 mm
 and 70 mm imbibition films (dyed by the Technicolor process).


 It's important to know exactly what types of film are in your
 possession because nitrate fumes and fire are a threat.
 Conditions that may only marginally harm the acetate films can
 cause a nitrate base to become very dangerous. Unless you can
 detect some deterioration, you may have a hard time
 differentiating nitrate from acetate base films. Edge
 identification may establish the difference the easy way.


 You can use ultraviolet lamps to identify EASTMAN Triacetate
 Films by the resulting fluorescence. A different identification
 tool is your nose. Cellulose nitrate has a characteristic acid
 odor, similar to that of nitric acid. This odor is unmistakable
 when a quantity of nitrate film has been stored, especially in
 a nonventilated area.


 Evaluating the Extent of Deterioration
 The nitrate film you have in storage may be middleaged, but if
 it was properly stored, it may be quite usable. However, if it
 was neglected, it may be showing signs of early deterioration.
 One way to determine the extent of deterioration is to look at
 the color of the base. If it's yellowish, or even amber,
 sulfiding has begun because of silver in the emulsion and some
 yellowing of the gelatin. The confirming test is to see if the
 film base is brittle and breaks easily on being bent in half,
 especially with the emulsion side out. At this stage, the
 gelatin is probably soft enough to dissolve readily if the film
 is wetted.


 If these symptoms of decomposition are found, handle the film
 with care and keep it dry. Duplicate it soon after inspection,
 drying, and cleaning, because buckled film and sticky gelatin
 may make duplication later more difficult or perhaps
 impossible.


 Spontaneous Combustion
 Spontaneous combustion is self ignition of combustible material
 through chemical action (as oxidation) of its constituents. It
 develops from knowable conditions, such as deterioration, and
 with proper observation and care, you can prevent a chemical
 reaction. Nonpreventive measures, whether it's in hay, oily
 rags, or nitrate film, can result in a fire. With the
 information given in this section, you can prevent the threat
 of spontaneous combustion.


 Apparently, fire isn't caused by cellulose nitrate in good
 condition. But in the advanced stages of decomposition, self
 ignition takes place at sustained temperatures only slightly
 above 38°C (100°F). If undetected, heat producing deterioration
 and high temperatures, with consequent heat buildup, coincide.
 Such combustion isn't nearly so spontaneous as its name seems
 to imply!


 Storage Vaults and Conditions
 Carefully examine all the materials known to be on nitrate
 base. Detecting unstable nitrate film is by far the most
 important way to preserve this material. If decomposition isn't
 found quickly, complete destruction of the film record may
 result. Spot inspection only needs to be done once a year if
 you follow the recommended storage conditions, and once every 3
 months if adverse conditions exist. Any nitrate film that is
 badly buckled or sticky is in an advanced stage of
 decomposition.


 You may be able to duplicate some of these badly buckled or
 deteriorated films, or they may yield a fair quality print.
 Urgency is the word. If the film base is heavily stained and
 moisture from our breath makes the gelatin slightly sticky, the
 negatives or prints must be duplicated within 2 years while
 maintaining proper storage conditions.


 Never wet a decomposing nitrate base negative; the gelatin may
 be readily dissolved. If you must remove surface dirt, use a
 quality cleaner carefully. Many old negatives have an
 iridescent dichroic or silver sulfide stain, usually on the
 surface of the gelatin. This is a further sign of old and
 deteriorated film.


 Store these negatives only in small quantities and in different
 locations. The production of chemical vapors and heat from
 large concentrations of nitrate films demands special storage
 conditions with a special exhaust and ventilation system. This
 storage area should never be near safety films.


 Never store any nitrate base materials in sealed containers or
 without ventilation. Such dead storage simply increases the
 rate of decomposition. Pack the reels loosely in ventilated
 metal boxes or cabinets, and store them in a room apart from
 all other photographic materials. Do not let the storage area
 temperature exceed 21°C (70°F). If you achieve a lower
 temperature without increasing relative humidity above 45
 percent, that s even better. Relative humidity below 40 percent
 retards decomposition even more, but makes the film more
 brittle.




 Help for Owners of Nitrate Base Film
 Nitrate base films have been out of common use so long (since
 about 1951-52) that expertise in handling them is not commonly
 offered, but there are facilities that do offer this service.
 Unless you are an expert concerning the characteristics of
 nitrate films in various stages of decomposition, don't unroll
 the films. Let the experts do it. For help determining the
 historical (not monetary) value of any material on nitrate
 base, contact a local historical film association or
 International Film Archive, FIAF Secretariat, rue Franz Merjay
 190, 1180 Brussels, Belgium. If they can't help you, they'll
 direct you to someone who can. If the film has value or you
 decide to have it duplicated, even if it isn't unique, one of
 the film archives can give you advice on the procedures for
 arranging duplication.

 Dave Edgar
 Cinematographer/Steadicam operator
 [log in to unmask]

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