Chapter 1 - Film

 

If you ask five different people what film is, you’ll probably get five different answers.
The only one that matters is that film is a thin, flexible plastic strip coated on one side
with gelatine emulsion.
      

The Plastic Base
The first cinematic film was cellulose nitrate, generally called ‘nitrate’. It was very
flammable and had to be stored and handled with great care. By the 1950s nitrate
had been replaced by cellulose triacetate, or ‘acetate’, known also as ‘safety film’
because it did not pose the same dangers as nitrate. Over time, acetate warps,
buckles, curls and becomes brittle.

 

For the past 30 or so years, polyester has been used as the plastic base. It is immensely
strong and safe. It takes longer to break down and go brittle than nitrate or acetate.
But it is affected by heat, dust, excess humidity and dryness, is easily scratched and
damaged and will curl, warp and buckle, just like its predecessors.

 

Most 16 mm films available for screening are polyester based, but older films which
have not been transferred to polyester are acetate, which may be brittle and need
careful handling. Very few 16 mm nitrate films now exist outside archives, where
they can be given the care and attention they need.

 

The Emulsion
The gelatine emulsion is soft, soluble and easily scratched. The emulsion carries
the photographic images in units called frames, which are separated by frame lines.
The images comprise varying quantities of silver, for black and white film, and layers
of dye for colour. The various chemicals all deteriorate over time, but generally black
and white films are more stable.The emulsion also carries the optical soundtrack,
which is a wavy line that travels along one edge of the film. The line of holes along
the other edge are called perforations. These are accurately punched in the film to
engage the projector’s sprocket teeth as they rotate, so the film can be moved
through the projector at a constant speed.

 

YOUR TURN
Unroll some film from a reel until you can see some images.
Look at both sides and see if you can pick which is the emulsion side.

TIPS:

1. The emulsion side is generally duller.

2. The old test was to lick your bottom lip and quickly touch one side of the film
to it. If the film tended to stick to your lip that was the emulsion side. If it did
not, the emulsion was on the other side. If you try this, be careful. Unless you
are quick, the emulsion can adhere to your lip and be difficult to remove.

Storage
Storage conditions for film are critical. Individual reels should be stored in their own cans
and kept in a cool, dry place with minimum temperature fluctuations. Black and white
films should be stored at between 15° and 18° C. The ideal temperature for colour
film is much lower, 8° C degrees or less. Water is a serious hazard to film and can
destroy it. The presence of even small amounts of moisture encourages the growth
of moulds that attack the emulsion and the film base. Refrigerators are not recommended
for film storage, as their internal atmospheres contain high levels of moisture. Different
experts have divergent views on how film should be stored on the reel. Some say it
should be wound on tightly. Others say it should be wound on at fairly loose tension
for storage then rewound at higher tension before screening. If you are preparing to
store film long term, it is arguably better tightly wound, as this is likely to help prevent
moisture, dust and moulds entering spaces created by a loose wind.
(Refer also to information on vinegar syndrome in Part 3.)