Acetate (safety) film and nitrate film don’t mix

Or do they?

For a librarian, archivist or anyone that manages a collection of visual media, it’s important to know if you have Acetate-based (or “Safety”) media mixed in with your Nitrate-based film. This is relevant for two reasons:

1. Acetate-based Safety film, when it begins to break down, can emit gasses that accelerate the decomposition of Nitrate-based films.
2. Culling out any Safety film can save money. Maintaining Nitrate-based stocks in storage is heavily regulated and quite expensive. Why pay Nitrate storage costs for Safety film storage?

At PRO-TEK, we have had situations where a client was preparing to absorb the cost of Nitrate storage and we discovered Safety mixed in as well. To understand how and why you might have Safety hiding in your Nitrate collection, we have to look at some history.

Transition from Nitrate to Safety in Commercial Film

From the advent of photography in the 1800’s until the early 1950’s, most commercial movies and still photography used Nitrate-based stocks, but Safety stock was also in use during its infancy. In 1897, Pathé Films held a public showing of movies in Paris displaying the new technology for a crowd of VIP’s and government officials. The Nitrate-based film and projector caught fire, killing at least 140 people. New laws and restrictions resulted and Nitrate became a heavily-regulated process for commercial use only. The flammability of Nitrate-based film stock started a world-wide search for a safer alternative.

Eastman Kodak was experimenting with Safety stock as early as 1906. Early Acetate-based Safety stock was an inferior way to capture and display images, so studios and commercial content creators were reluctant to switch over. However, safety was a sought-after quality for the home market.

Pathé also had experimented with Safety film and by 1912, they were selling a camera and projector for home use and hobbyists with a non-flammable Safety stock that was 28mm wide. Around the same time, Thomas Edison also introduced a home and hobbyist system, The Edison Home Kinetoscope, which used Eastman Kodak Acetate-based Safety film. Safety stock was desirable for the home market because it lacked the flammability of Nitrate, especially helpful when projecting home movies on balky or poorly maintained projectors set up in the den or living room.

3-strip Technicolor camera from the 1930s. (Image courtesy of Marcin Wichary [CC BY 2.0], via Wikimedia Commons.)

3-strip Technicolor camera from the 1930s. (Image courtesy of Marcin Wichary [CC BY 2.0], via Wikimedia Commons.)

Commercial studios were willing to assume higher risk, so it would not be until 1951 that major commercial movies were finally being shot exclusively on Safety, and Nitrate was fully phased out. There were some occasions when the studios or commercial entities would shoot on Acetate, well before the commonly understood cutoff date of 1951. The use of Acetate usually intersected with the need to capture images in color, not black and white.

The Advent of Technicolor

Color film photography was highly desirable by the public, and manufacturers experimented with many different processes. Technicolor became the industry standard for commercial color-film photography by the early 1930’s. Three strips of black and white Nitrate film loaded into a camera would eventually yield beautiful color prints, but the Technicolor 3-strip camera was a giant, massively heavy machine, as it had to accommodate three pieces of 35mm film running at the same time.

Eastman Kodak manufactured all of the film that Technicolor used and the two companies had various patents and exclusivity arrangements with each other. Kodak had been experimenting with a single piece of color film stock, something that could be loaded in any camera, as opposed to the Technicolor 3-strip system. This was monopack, or “Monopack” with the ‘M’ capitalized, as it was an exclusive process that Technicolor had trademarked.

Kodak, under its agreement with Technicolor, could only sell it’s monopack to the general public in 16mm, so it couldn’t compete with Technicolor’s 35mm “Monopack”. This 16mm film was marketed as Kodachrome and it’s bright, vivid color images still amaze when we view old home movies shot on this stock. More importantly, it was Safety-stock.

As Kodak perfected its home-use color stock, it passed the processes on to Technicolor and eventually, the 3-Strip camera was phased out and 35mm Monopack became the capture-medium of choice for color. When the so-called “Monopack Agreement” between Technicolor and Kodak ended in 1950, Kodak expanded its color-photography processes and they became widespread among many companies. Although it never achieved the superior color image quality of 3-strip, Monopack was improved and simply became known as color film stock. The word Monopack eventually faded away and we were left with Kodachrome for the home market and a wide variety of color stocks for commercial use in 35mm, 65mm, etc.

Why Safety Stock May Be Hiding Among Nitrate Stock

So, why is it that archives and libraries might have Safety stock hiding withing their Nitrate collections? Pre-1950, if a studio was making a film that demanded lighter, more nimble cameras, they would face a challenge. For example, what if the movie was about military pilots and featured real flying sequences? How could anyone safely fit an enormous 3-strip Technicolor camera into the cramped nose of an airplane? The solution was to use smaller cameras loaded with Monopack in either 16mm or 35mm. The rest of the movie – the portions shot on a stage or at least on terra-firma – was shot in the superior 3-strip Technicolor. Later, during post-production, the Monopack would be converted to Technicolor.

After the airplane with the smaller camera landed, the single piece of full-color Safety Monopack would be sent to the lab and converted into three strips of black and white, color-separated film. Those color separations would be made with Nitrate film stock. These new versions of the sequence would then be integrated into the rest of the already-shot film, so the editor could create one whole, original negative of the finished film, without any variations in the media formats. These new separations would be called “Original Negative”, but in fact, they were dupes. The original would still be the Monopack that was loaded into the camera and used to shoot the sequence.

Years later, there are archives that may have the original negative to a particular movie and they may be well aware of the fact that this negative is on Nitrate stock, but they may not be aware that if they also have the original Monopack, then they also hold Acetate-based material for the same title.

This may seem trivial but with the enormous costs of maintaining any Nitrate-based material, not only in dollars but in training for personnel and keeping up with fire and building code requirements, it might be good to know if you have material mixed in that can be safely removed and stored elsewhere.

At PRO-TEK, we have received collections and handled projects for clients that were thought to be exclusively Nitrate-based projects. Often however, we have seen Monopack mixed in with Nitrate. It’s easy to mix the two and the reason is because the first few feet of film can be deceptive. Often, the Monopack may be wrapped or even spliced with Nitrate based leader. One can easily roll a few feet into an element and find the word “Nitrate” stamped on the edge of the stock. Keep rolling in and when you get to the actual shot or shots, they are on Monopack that is clearly stamped, “Safety”.

Remove the Nitrate leader and you suddenly have an element that is much less costly to work with or store.

To learn more about Nitrate and Acetate (Safety) film archiving and preservation, see the following articles:

Preserving Nitrate and Acetate Motion Picture Film Collections

Nitrate Film: If It Hasn’t Gone Away, It’s Still Here!


Danny Kuchuck
Danny Kuchuck is Film Technician and Project Manager at PRO-TEK.
Danny Kuchuck

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