What causes your film to decay? First we need to look at what film is. Film is a plastic base (cellulose acetate) with a gelatin emulsion layer over top of it. The Emulsion holds the image left over after exposed parts have gone. Old black and white film is simply silver particles or commonly referred to as silver crystals. Depending on the time of exposure onto the film, more exposure meant more washed away crystals. When the film was developed, the processing removed the exposed areas to let light through. This negative image allowed the image to look correct when light was projected through it. Later versions of film emulsion holds color dye. This created color images to pass through the light. This is true for all types of film including 8mm, 16mm and 35mm film.
What we can do to preserve film is keep it cool and dry. Heat and plastic is not a good combination. Cooler temperatures make for better long term conditions. If you have ever had your film get stuck in the gate of a projector when the bulb is warm, you have no doubt seen your film melt before your eyes. Moisture is also a long term killer of film. Just like so many things in life, water damage is fierce, quick and usually unfixable. But over the long term, the decay of film is accelerated with moisture. We have found that some metal cans do a good job of keeping the film dry and others do not.
The overall decay of the film is a process commonly known as vinegar syndrome. If you have ever smelled this decay, you know where the name comes from. It stinks (and is not good for you either)! Vinegar syndrome is the creation of an acid from the heat/moisture chemical reaction happening with the cellulose acetate. The decay causes 3 key things to happen that make the film unusable. First is the curling or shrinking of the film. Second is the drying up of the film making it brittle. Third is the loss of the silver or dyes. The overall process can take a long time, accelerating after a certain point.
Our experience with the film decay is extensive. In order for us to transfer the film, it needs to not crumble and break into pieces and needs at least a little bit of flexibility. Fortunately, we don’t use machines with sprockets, so it is less abrasive. But it still needs to bend enough to get through the machine. Having a curve that’s created by the decay can be overcome if the film is still soft enough to uncurl as it passes over the gate of the machine. It needs to do this so the image can flat to allow for the focus of the film to be correct and also so that the sprocket holes can be viewed correctly by the camera and the sensor. The camera and sensor are looking for the sprocket holes to be in a particular place, if they aren’t, the machine cannot sync to camera to the film frame. If dried up emulsion with silver and dye is flaking off the film, there is nothing to fix that. Sometimes the running of the film through the transfer machine could be the very last time the film with ever play because the images are falling off as it’s moving.
The storage of the films in a cool, dry area are the absolute best. Do not rely on the fact that the container may be closed. Some containers are just cardboard and others are made out of tin or medals that are not sealed tight. Ziplock bags are OK as long as there is no moisture in the bag. Locking moisture in can be just as bad as keeping them in bad long term storage.
The final thought would be to use caution with film cleaners. If the integrity of the emulsion is not good, wiping the film with the cleaner could potentially damage the film or wipe away the image. Having some dust is better then having no image.