Nitrate and acetate film restoration

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Film collectors and content owners often contact us with questions about restoring film—whether it’s nitrate or acetate (safety) film—that has begun to decompose. While each case is unique and should be assessed by a professional, the following are a few considerations or “rules of thumb” to guide your decisions and next steps of action.

First some brief but important context. All photographic film is comprised of emulsion on top of a base:

  • The emulsion is the photosensitive material that contains the imagery.
  • The base is a transparent substrate that serves as the support layer and is most prone to degradation, and as the base layer goes, so goes the emulsion or the image, which will eventually become useless or disappear.
  • Three materials have been used to create the base layer—in chronological order they are nitrate, acetate and polyester.

This article will discuss film restoration and preservation for nitrate and acetate substrates.

Nitrate film restoration

If any of the items in your film collection date back prior to 1952 or so, you may have nitrate film. Film that is old enough to be on nitrate substrate has intrinsic historical value, let alone any potential monetary or creative value.

One advantage of a nitrate base is that when it starts to decompose, it may not shrink or warp as badly as acetate film can. It often stays pliable, which limits cracking and warping, and it may not shrink as much or as quickly as it decomposes.

However, while decomposition may happen more slowly with nitrate, it is a guaranteed, continuous process, so damage will only get worse over time. The gasses emitted by the decomposing nitrate film base will eventually attack the emulsion and eat away at the image. So, you may have a decent-seeming piece of nitrate film that is not too warped or shrunken, but find there are places on the roll where the image is “melted” or unrecognizable! No magic can restore images that have completely disappeared, and nobody wants gaps in their film content.

Another grave issue with nitrate, and one of the main reasons it was replaced and is no longer used, is that it’s highly combustible and requires special handling and storage. This should be your overriding concern. If you have identified nitrate film in your collection, I encourage you to contact us or other nitrate film experts for consultation and guidance.

Acetate film restoration

Acetate or “safety film” as it is known, was the technology that replaced nitrate in commercial filmmaking. It had been used for several decades in the amateur home movie market, but not until the early 1950’s was it adopted by the professional filmmaking community.  While acetate film is considered safer and easier to work with, decomposing safety film can present a different set of challenges from nitrate. In addition, it can be more difficult to restore than nitrate.

Signs of safety film decomposition

When the base of safety film starts to decompose, we call it “vinegar syndrome” and the entire film may start to curl, warp and shrink.

Vinegar syndrome is the chemical reaction that occurs when acetate deteriorates, which causes deacetylation and the formation of acetic acid, producing a distinct vinegar odor. Besides smell, we use specially treated paper that changes color in the presence of vinegar syndrome to indicate the severity of degradation and detect early deacetylation.

Vinegaring doesn’t necessarily mean your film is beyond rescue; however, it does signal that deacetylation is taking place and that you need to act. The process is usually continuous – once started, it can’t be stopped or reversed. And to make matters worse, it is an autocatalytic process, meaning it feeds on itself and accelerates.

We can use chemical dessicants to trap the vinegar gasses as they escape to keep the problem from spreading. And storing film in freezing or near-freezing conditions can also halt the spread of vinegar syndrome. These are services we offer that can and do slow the decomposition process down greatly, giving you more time to assess your collection and begin scanning.

While the damage is really only happening to the base of the film, the emulsion deteriorates along with it, causing damage to both layers. Damages include:

  • Curling and warping
  • Shrinking
  • Cracking
  • Fading, especially problematic in color film

Some image damage can be corrected in digitization. Preservation scanners with adjustable film tension and other specialized features can handle some compromised film. The process must include gentle care and handling—literally the white glove treatment, since sweat and oil from even “clean” bare hands is another factor that leads to film degradation.

For collections that include color motion and still picture film, color fading caused by spontaneous changes in the color dye chemistry is a concern. You can tell color film deterioration by color changes, and you should take action if you see them, since that’s a sign that color fading has begun. For example, with positive prints, if you see a pinkish cast, it’s a sign that the cyan and yellow dyes, which fade more rapidly with older stocks, have begun failing.

The only way to guarantee a long, useful life for color film is to keep it in long-term cold and dry storage, like our facility in Burbank. We can’t emphasize enough how important cold storage is, and we are happy and proud to be working with Paramount Pictures to develop below-freezing storage for the studio’s film collection.

The role of digitization in film restoration

Professional digitization can restore much of a film’s imagery by combining a little technology, a little art and some understanding of the time, place and context. We have Photoshop experts who can make cracks and other blemishes magically disappear in the digital version. Depending on the intentions and needs of the collection owners, digital imagery can also be enhanced. For example, with permission, we have done touch-ups like increasing contrast to meet the film owner’s requirements.

According to Jim Harwood, Director of Operations at our facility in Burbank,

“Needless to say, the best results come when there is little or no degradation. We often have a piece of film that may look okay when you hold it up to the light and just look at it. The entire image may be intact, but the base may be so shrunken or warped that scanning the image becomes a huge challenge. Modern film scanners are quite forgiving, but they cannot do the impossible.”

If your film is beginning to show signs of degradation—fading, curling, warping, etc.—time is of the essence. Deterioration does not stop. Without immediate restoration followed by a change to proper long-term storage, the environmental factors that caused the early signs of damage will continue, leading eventually to irreparable damage and permanent loss of the film’s content.

Storage conditions – aim for cold and dry

The single most crucial thing you can do to prevent deterioration is to store you film collection in a proper facility. I would say without that, there’s really not much sense in bothering with it at all, unless you have a short, immediate timeframe in mind.

The big three destroyers of film are the 3 H’s:

  1. Heat
  2. Humidity
  3. Handling (excessive and without proper care)

At all costs, avoid storing film in prolonged heat or humidity. Heat speeds up and contributes to vinegar syndrome and color fading, while damp conditions cause film to stick together and mold may grow, ruining the emulsion. Rough or excessive handling of the original film also leads to deterioration.

Any space that is regularly inhabited by people is inadequate for film storage, which requires cold, dry air with no deviation. When we take people on tours of our film storage vaults, we suggest they wear a jacket or sweater!

In addition to keeping the storage environment cold and dry, professional film storage vaults take other environmental threats into consideration like fires, storms, earthquakes and theft.

An ounce of prevention is worth a pound of cure. In film preservation, it may be worth a ton of cure, because film degradation is inevitable, not a question of if, but when. Learn to recognize the signs. More importantly, make it a priority.  Getting ahead of it will not only save money, it will greatly improve your chances of keeping your film collection preserved for viable future use.

Danny Kuchuck

Danny Kuchuck

Danny Kuchuck is a filmmaker, writer and archivist living in New York. He is a former film technician and project manager for LAC Group, and prior to that, PRO-TEK Vaults.
Danny Kuchuck

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