A Year in the Life of Audiovisual/Media Preservation in Illinois: Film Identification, Film Condition and Film Preservation

Beth McGowan, PhD, MLIS

​Film–whether motion picture film, cut sheet film, microfilm, (either microform or microfiche), and amateur film – is generally at great risk in most collections. These four kinds of film come in three major materials: nitrate, acetate and polyester. Of these three, most attention will be paid to acetate because it is fragile and common. In contrast, the earliest of these materials, nitrate, while fragile and flammable, is relatively rare. The most recently developed material of film, polyester, though common, is a very stable material and requires less attention.

The four major steps to film preservation are locate the film, identify its material, assess its condition, and choose a preservation storage method based on best practices for condition of film and institutional feasibility. Unfortunately, none of these is easy.  

Identification

To initiate a preservation plan for film, an institution must first locate film in its collections and identify the material of the different kinds of film. How to do this?  Dating is a good first step. Below is a table that tries to catch dating for four major types of film in various materials.Film, specifically moving pictures, cut sheet film, microform/microfiche, or amateur film, comes in three materials that correspond to roughly three major periods. From 1890 to mid-1920s, all film was nitrate film. Following the mid 1920’s came a period of 30 years when nitrate film co-existed with triacetate film. The triacetate film (often labelled safety film) was created to combat the flammable nature of nitrate film. Acetate is less flammable, but though thought to be more stable for preservation purposes than nitrate, it shares many of nitrate’s durability issues. Nitrate film finally disappeared from production in all types of film in 1951. Between acetate’s development and the mid-1950s, acetate’s durability issues became clear, and a third material, polyester film, was introduced in cut sheet film, amateur film, and microfilm.  While acetate continued to be used for many years in motion pictures because it was easier to splice than polyester, by the early 1980s it ceased to be used in other formats such as microfilm. Acetate and polyester both continue to be produced, though polyester truly is more durable. Therefore, for most organizations, acetate film needs most attention in terms of preservation.

Physical Characteristics and Physical Condition of Film

Beyond identification by the date material was created, another way to identify a type of film is to examine its physical properties. Nitrate and acetate film share basic construction characteristics: they have several layers and the integrity of these layers are central to the condition of the film. (For more information on the layers of film and their roles in film, (See ”Film Preservation for an Academic Collection” CARLI Workshop October 13, 2008.) This makes them similar in some significant physical ways that differentiate them from polyester film. They are both easy to tear (and consequently to splice) while polyester is hard to cut or to tear and therefore to splice. Both nitrate and acetate are dense, not translucent in reels while polyester film allows light to pass through it. Polyester film, when placed between polarizing sheets of plastic, reveals birefringence while neither nitrate nor acetate does.

In addition, film deterioration also provides a means to identify film. As most of the film that needs preservation in most collections is acetate, acetate deterioration needs to be identified. These are its major characteristics: a vinegary odor caused by the actual creation of vinegar as the film decomposes, brittleness, shrinking, bubbling on film surface, and a pink or blue coloration. （For a full explanation of the chemical processes involved, see James M. Reilly, “Basic Strategy for Acetate Film Preservation” in Microfilm & Imaging Review September 2002 117-13）In addition to using the senses to identify deterioration in acetate film, there are products, notably acid detector strips inserted into the film enclosure,  that test the condition of film by testing its acidity. Consultants may also be hired to monitor the condition of film collections.

To do determine birefringence: Place film between two layers of polarized plastic sheeting. If then viewed through transmitted light, colors like “oil slicks on ponds” will appear. (Reilly, IPI, 21)

Preservation

The physical condition of film, whether nitrate or acetate, dictates preservation needs. If a film has already begun to chemically deteriorate, it should not be stored at room temperature.  Once the deterioration process begins, it feeds further decay. Generally, the optimal preservation strategy requires colder and drier conditions.  While there is no ideal temperature, colder is better. Relative humidity  is best kept between 20% and 50 % humidity with the lower end of the spectrum (20-30 %) being dramatically better for long term storage as a low relative humidity also keeps pollutant levels low. Finally, enclosures should be chemically inert. How individual institutions create these conditions depend upon resources. Some use microclimates; some attempt more macro fixes.

In any case, a great deal of very practical and precise research has been conducted on the optimal conditions for varying degrees of deterioration. For precise measurements of speed and progress of deterioration already begun and best storage practices, see the “IPI Storage Guide to Acetate Film” written by James M. Reilly. Accompanying Reilly’s guide is a very handy set of tables and a wheel to determine storage needs of acetate film based on present conditions. It should be clearly understood that no storage methods can restore film, it can only retard further damage.  This guide can more or less double as a guide on the preservation of nitrate films as well.

CASE STUDY

Throughout the year, Anne Thomason from the Donnelley and Lee Library at Lake Forest College and Patrick Brown from Morris Library at Southern Illinois University will be sharing their experiences with audiovisual preservation. Below are questions regarding motion picture film, cut sheet film, microfilm, either microform or microfiche, and amateur film.

Resources

Works Consulted

Bigourdan, Jean-Louis and James M. Reilly. "Effectiveness of storage conditions in controlling the vinegar syndrome: preservation strategies for acetate base motion-picture film collections.“

Forbes, David. “Film Archives: A Decaying Visual History” in African Research and Documentation 110 (August 2009): 37-43.  Library Literature and Information Science. Web. 13 May 2016.

Frick, Caroline. “Separate but Equal? Bolstering Audiovisual Preservation” Preservation, digital technology & Culture 43.1/2 (April 2014): 20-25. Print.

Reilly, James M. “Basic Strategy for Acetate Film Preservation” Microform & Imaging Review 31.4 (September 2002): 117-130. Print.

Reilly, James M. IPI Storage Guide for Acetate Film Rochester, NY: Image Permanence Institute, 1993. 

Additional Online Resources

Dean, John F. Cornell Library Conservation and Preservation Tutorial. Ithaca, NY: Cornell University Library December 15, 2004.

Film Preservation Guide: The Basics for Archives, Libraries, and Museums. National Film Preservation Foundation 2004.

Image Permanence Institute. Rochester, NY: Rochester Institute of Technology 2016.

National Film Preservation Foundation.

Northeast Document Conservation Center (NEDCC).

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