All the types of film have three basic components: a supporting base that is ideally “transparent, free from imperfections, chemically stable, not sensitive photographically, and resistant to moisture and processing chemicals while remaining mechanically strong, resistant to tearing, flexible, dimensionally stable, and free from physical distortions” (Kodak, Film Care, 16), a very thin light-sensitive emulsion layer (positive and negative) that consists of suspension of silver salts in gelatin, and adhesive substratum also consisting of gelatin, and a varnish layer with a solution of 1% nitro-cellulose to prevent curling (Volksmann, 5). Celluloid film may not have been the absolutely flawless base the Eastman Kodak Company was striving for, but undoubtedly it was more convenient, durable, and flexible than any other film preceding it. The most prominent difference between types of film over time is their bases, which in this case, nitrate-based film is being studied. The main ingredients of cellulose-nitrate film are implied by the name; they are gun-cotton or pyroxylin which is prepared by treating cellulose with a mixture of sulphuric and nitric acids, and wood alcohol (Talbot, 52). The film also has a high silver content to create rich tones for black and white images, which is one of its greatest strengths. Despite the initial success of nitrate-based film, its impressive properties that advanced the film industry are also coupled with problematic drawbacks. The two major concerns with cellulose-nitrate film are that it is highly flammable and decomposes at fluctuating rates, overall making the material somewhat unpredictable and hazardous without the implementation of safety precautions.

First, cellulose-nitrate film is very combustible because its chemical composition is similar to gun-cotton which is used to manufacture explosives. Therefore it can burn rapidly and if conditions are right, spontaneously self-ignite (Slide, 1). New raw stock has an ignition temperature of 130 degrees Celsius or 266 degrees Fahrenheit and as the film decays that temperature decreases (Volksmann, 6). There is also no means of extinguishing a nitrate film fire because it can produce its own oxygen, so using water for example, is pointless.

Second, cellulose-nitrate film is unstable because of its Nitrogen compounds and as a result is in a perpetual state of decomposition. Attempts can be made to delay the exponential rate of decay, but “even under the most favorable conditions nitrate film decomposes” (Volksmann, 6). The most telling attribute of this biological and chemical process other than visual, is the pungent odor of the nitrate gases being emitted that are lethal for film reels and humans alike if permitted to linger (Volksmann, 23). Otherwise the decomposition of nitrate-based film is visually and tangibly captivating in a disturbing way. In the first stage, the silver image undergoes an amber discoloration and fading. In the second stage, the emulsion becomes sticky and portions of the film become soft. In the third stage, gooey, blistering bubbles appear and pop, emitting the noxious fumes of the nitrate gases. In the fourth stage, the entire film reel congeals and is welded into a solid mass covered by a viscous froth. Finally in the fifth stage, the film disintegrates into a fine, dry, acrid powder that is highly volatile (Volkmann, 6 and Kodak, Storage & Preservation, 15). Evidenced through this sequence, it is clear that the film is only salvageable for preservation or copying up until it becomes rendered useless by stage two. While decomposition is simple to detect in the other phases, the first phases are the most important to check because the type of decomposition is “autocatalytic” meaning that the “chemicals released accelerate the reaction”. The more gases emitted and allowed to remain in contact with the film, the faster it breaks down. Therefore, “the extent of the decomposition under any condition is not proportional to the age of the film and it is therefore difficult to detect in time” (Kodak, Storage & Preservation, 14). Ranges in the rates of decay depend on different factors, many of which can be controlled through artificial climates and careful maintenance beginning at the initial steps of the film’s manufacture (all of which is discussed in CONTAINERS). Accordingly, some nitrate-based films have survived for a century, while others are lost in less than a decade.

The most typical film sizes are 35mm or 16mm gauge; nitrate-based film is used exclusively for 35mm gauge, mostly black and white, but could sometimes have color added (Volksmann, 5). One of the advantages of this fact is that it makes it a little bit easier to identify nitrate film because it was only manufactured with one gauge. The size of the images obtained on the film strips is 1 3/8” wide by ¾” deep (Talbot, 25). It is important to maintain these dimensions of perforation and image to attain quality performance and to prevent further damage of the film itself during processes like projection or copying. However, due to the film’s properties, exposure to certain conditions can unfortunately alter otherwise standard characteristics.

Like other materials, cellulose-nitrate film expands when heated and contracts when cooled (Volksmann, 22). Therefore a consistent, steady temperature is desired. The properties of the emulsion layer and film support also depend on the amount of moisture they contain and react to the moisture content of their surroundings to reach equilibrium, either giving up moisture if situated in dry air or absorbing moisture when in a damp setting (Kodak, Storage & Preservation, 11). Likewise, as will later be explained, particular relative humidity levels are also preferred because otherwise unfavorable defects result. For example, too high a relative humidity fades and discolors, increases shrinkage, produces mottle and ferrotyping (glossy marks), leads to softening and sticking of the emulsion, promotes fungus growth, and speeds up decomposition, while too low a relative humidity can increase susceptibility to static markings, brittleness, and curling (Kodak, Storage & Preservation, 13). Additionally, without proper ventilation and cleansing of the air, dust and dirt settling on the film surface when it is moist or wet pose a threat of smudging or scratching the images. All of these effects are detrimental for optimal viewing and operation and therein lies the task of providing conditioned containers.