Film Assessment, Part 2: A Long and Winding Road

Film assessment station

As Helen Bailey's excellent post described, the Preservation Services Department has taken a large selection of the college’s film archive to assess for damages. Of the three types of film stock (Cellulose Nitrate, Cellulose Acetate, a.k.a. "Safety" film, and Polyester, in chronological order) we are generally working with Acetate. Any remaining Nitrate films in the collection should have been dealt with already, as they are serious fire hazards, especially when stored improperly. For an example of just how serious the hazard is, check out this video of Rayle Archive and Screening Room doing a test burn of nitrate film (and please do not try this at home!)

After confirming that we are working with Acetate film stock, the next thing to be done is measure the Acetate decay. This is the vinegar odor Helen described in the previous post. We do this using AD strips, which produce a color coded result. The result ranges from 1 to 3, with anything above 2 being measured as “extreme Acetate decay.” While extreme decay cannot be reversed, it can be slowed by improving storage conditions.

AD strip and indicator

The next measurement to take is shrinkage. This, too, is a symptom of Acetate decay, but it can also be caused by excessively dry storage conditions. This is done using a shrinkage gauge. Any shrinkage higher than .08% requires a laboratory to copy the film, otherwise it may be permanently damaged during projection. Shrinkage past 2% will be nearly impossible to fix even in the most advanced film labs.

Shrinkage gauge

Next comes the fun part. The film is placed in a manually-operated rewind bench. A viewing glass is used and a lightbox is placed underneath to better view the film. Then we wind the film through once onto a separate film core, examining all the splices with the viewing glass and feeling for damage around the edges.

Lightbox and viewing glass

Here we are looking for any kind of visible damage. This can range from mold on the film itself to poorly done or degraded splices. Another common problem is broken sprockets, which can easily cause problems down the line when trying to project these films.

Example of undamaged film splice

All the various damages are then catalogued in a spreadsheet. At this point the film has to be rewound onto a new film core. Improper winding can cause damage to the film during storage, so with a manual rewind like this it can take several tries to get it right. It’s important to wind evenly, guiding the film onto the core in a consistent way. If the film is wound haphazardly for storage there will be pressure on different areas of the stock, causing warping and damage.

Severely warped film

From here, we should have a clear idea of exactly how damaged the film is. As we make progress through the current selection of football reels we will be figuring out storage and repair solutions to best preserve Dartmouth's films.

More work to be done!

Written by Ryland Ianelli.