Why nitrate?

[Jeff Joseph <sabucat@SABUCAT.COM>]

This was written by Richard W. Haines, and is reposted here with permission.

A number of people keep asking me why Kodak used nitrate base for film for
fifty years when it was so flammable and dangerous. I just read a new book
on the history of plastics and here's why...

Nitrocellulose was not designed to be a motion picture medium.
Nitrocellulose was developed simultaneously by British and American
inventors (resulting in extended lawsuits) by combining cotton and nitric
acid which formed a hardened plastic. It was created to replace ivory,
which was expensive, and becoming scare since the Elephants were being
killed at a faster rate than they were reproducing. Initially,
nitrocellulose was used for billiard balls, cufflinks, combs and other
toiletry items, as a replacement for ivory since the cost of making it was
so cheap. Even then, it was highly flammable. If you hit a pool ball hard
enough it would explode. In fact, there's a gag in a Buster Keaton film
when he uses pool balls like grenades while being chased. Nitrocellulose
combs and cufflinks used to start on fire when people smoked near them.
Despite it's danger, it was so cheap to make many people liked it and it
allowed middle class people to afford the luxury items reserved for the
wealthy in the ivory days.

George Eastman was not a chemist but an innovative inventor. By trying
various formulas via trial and error, he discovered that by adding Banana
Oil (Amyl Acetate) to the cotton and nitric acid a transparent flexible
sheet of plastic resulted that resembled the 'fillem' on the top of spoiled
milk. The 'fillem' was shortened to the word 'Film' and thus the first
flexible nitrocellulose was invented. (A priest named Goodwin had also
developed it without Eastman's knowledge resulting in a $25 million dollar
judgment against him twenty-five years later) This nitrocellulose 'film'
was flexible enough to roll into 50 ft. spools and use in still cameras as
a replacement for the cumbersome glass plates used up to the 1880's. His
other innovation was precoating the rolls with silver and collodion so
anyone could take a photograph. To process it, you mailed the exposed roll
of film back to Rochester for processing and they made you the still
photos. The fifty-foot nitrocellulose roll was 70mm wide and took 24
exposures (without sprockets). Prior to this, photographers had to coat
their pieces of glass with the silver and process the glass plates
themselves. Thus, Eastman made the process of photography available to the
middle class. While the nitrocellulose negative rolls were highly
flammable, they were not dangerous to the consumer who merely used them in
the camera to take the 24 exposures. The Eastman Company did the rest and
the flammable negatives were destroyed after making the customer his
prints. The inherent danger was minimum unless you stored the pre-exposed
roll close to a fireplace.

Thomas Edison and his staff (along with the French) began to experiment
with the 70mm fifty foot rolls by punching sprocket holes in them and
taking successive exposures similar to Zoetrope toy images. To capture
movement, Edison ran his first camera at the rate of 48 frames per second.
This didn't give much running time so his mechanical wizard, Dickson, cut
the rolls in half, which made them 35mm and spliced them together in the
darkroom giving a 100-foot roll. Edison wasn't able to figure out a way to
project them so he created the peep show devise whereby the print of the
negative could be seen by an individual viewer looking at the frame through
magnifiers. The magnifiers were square, as was the frame which was
standardized at 4 sprockets high rectangular.  The amount of light needed
to see the frames was slight so there was little danger of the film
catching on fire from the illumination.

The film was very fragile when used in this manner so Eastman added Fossil
Oil (a by product of Whisky distilling) to improve it's tensile strength.
Thus motion picture nitrate film was a combination of cotton, nitric acid,
banana oil and Fossil Oil.

The French developed an operating projector with an intermittent movement
and shutter that gave smooth movement when illuminated by lime light
through a lens. However, the Lumieres and others thought that the rate of
48 frames per second made the film snap in the intermittent and determined
that a minimum of approximately 16 frames per second gave reasonably smooth
movement and less likely to break.
Projectors were simultaneously developed by Edison and others after the
French exhibitions. Unfortunately, as the industry for short subjects began
to develop the speed of the camera and projector was not standardized.
Thus, projectors contained a knob by which the speed could be adjusted
according the specifications on the print reel. Some directors like
Griffith and Chaplin shot at a slower rate than 16 frames per second which
made the images 'flicker', thus the term 'Flicks'. By the 1920's the rate
was increased to speeds between 20 to 24 frames per second. The speed of
sound of 24 frames per second was completely arbitrary and not ideal. It
happened to be the speed that synchronized the 33-rpm Vitaphone 16-inch
record. Earlier Movietone optical prints ran at a slower speed. The ideal
speed is between 26 frames per second (Cinerama) and 30 frames per second
(Todd AO) but these rare attempts to improve the smoothness of movement
were not adopted by the industry at large.

It was when the French and later American actually started projecting the
nitrate film onto large screens with brighter Carbon Arc illumination that
the problems started. The film shrank in the exchanges and if it jammed in
the projector you had a major fire on your hands. An early screening in
France at the turn of the century started a nitrate fire that killed a
hundred patrons and there were nitrate fires in vaults, labs and theaters
throughout its history. Di-acetate safety film was developed in the
twenties by Kodak and Pathe but only used for the amateur and
non-commercial markets because it shrank more rapidly than Nitrate. It
wasn't until 1948 that slow shrinking, slow burning tri-acetate safety film
was adopted by the industry and the nitrate phased out.

While nitrate has been a disaster archivally (it decomposes or explodes
when enclosed in a can in hot humid storage) and quite dangerous to project
if it jams in the gate, it was not designed for the use that Edison and
others adapted it to. It did have some attributes which was a clearer base
than tri-acetate and a high silver content which made the release prints
sparkle on the screen.

George Eastman was an odd character. He was a real loner and lived with his
mother in their mansion for decades, never marrying or having a family.
When he was diagnosed with a degenerative spinal disorder at age 76, he
shot himself in the chest with a Lugar.  I hope this answers those who
wondered why the industry used a gun power derivative for motion pictures
for fifty years.

Richard W. Haines