The cliched example that is always cited in explanations of the limitations on freedom of speech is that it’s not okay to yell “fire!” in a crowded theater. This is, of course, predicated on the assumption that there is no actual fire. Presumably, if there really is a fire in the theater it would be desirable to let people know. But really, how often does a fire actually break out inside a theater? In the early days of moving picture theaters, the answer is that it happened with sobering regularity.
An article in the April 20, 1918 edition of “Exhibitors Herald,” one century ago this week, chronicles that week’s fire report:
Why, then, were motion picture theaters so susceptible to the threat of fire? For a very good reason: the films they were showing were printed on a celluloid base that was extremely flammable. So flammable, in fact, that it is no exaggeration at all to describe it as explosive. The film stock originally manufactured by George Eastman and used by the movie industry during its first few decades consisted of a photographic emulsion layered onto a base made of cellulose nitrate. Just how flammable is cellulose nitrate? Here, have a look at this demonstration (don’t blink):
This form of celluloid was initially developed by a printer named John Wesley Hyatt (1837 – 1920) whose research into industrial chemistry had nothing at all to do with photography. His interest was in developing a new kind of billiard ball. With the increased scarcity of ivory driving up their production costs, the billiard ball company Phelan & Collander was offering a $10,000 reward to anyone who could invent a workable means of producing a synthetic billiard ball. Hyatt wanted to claim that prize, and felt he could do it through the chemical manipulation of cellulose.
The glucose molecule, as we know, can bind together to make sugar. But if it binds in a different way, in a long chain, it can make cellulose, a common form of which is cotton. If you soak cotton in a mixture of sulfuric acid and nitric acid…
IMPORTANT NOTE: Don’t do this. Seriously. There are videos online that show you how, but just don’t. The only way you should ever make nitrocellulose is in a properly equipped chemistry lab with a qualified chemist looking over your shoulder.
… and you evaporate/neutralize the acid, you get a nitrocellulose version of cotton known, with good reason, as gun cotton. Simply stated, what has happened is that a LOT more oxygen atoms have been chemically bonded to the glucose chain, which makes it a lot more flammable, as you can see in the video above. But apart from the explosive flammability, which makes it useful for munitions, another cool thing about gun cotton as opposed to regular cotton is that you can dissolve it using organic solvents. Then you can shape the dissolved nitrocellulose into various objects and evaporate the solvent. By exploiting this property, Hyatt essentially pioneered the use of plastics in manufacturing. Using this process, he did indeed create a synthetic billiard ball. Here’s a sample of his work from the Smithsonian Institution:
History does not record that Hyatt was actually awarded the prize, possibly because a billiard ball with potentially flammable properties was not exactly what the company had in mind. In any case, the celluloid that he had developed was subsequently utilized by an Episcopal rector and amateur chemist, Reverend Hannibal Goodwin (1822 – 1900), as a way of creating the magic lantern slides that he enjoyed using to illustrate his Sunday school lessons. The result of his labors was a base for the photographic emulsion that we would recognize as celluloid film. A similar formulation was later developed by Eastman’s chemists. Although Goodwin’s patent application carried an earlier date, he was, after all, an amateur with limited experience in the proper formatting of a patent application, so Eastman was able to obtain approval and begin marketing the new product before Goodwin’s patent received final approval. Consequently it was the name of Eastman that came to be associated with the introduction of celluloid film while Goodwin became a historical footnote.
Eastman’s cellulose nitrate film became the standard film stock in the emerging motion picture industry, used for both shooting the original negative and for manufacturing the prints that were shipped out to theaters for screening to the public. But remember, this is still a film stock made out of gun cotton. And when loaded into a theater’s projector it was being pulled through a film gate behind the projector lens mere inches away from an intensely hot arc light in the projector’s lamphouse. Each frame paused in the film gate for only a fraction of a second while being projected onto the screen, which was not long enough for sufficient heat to build up to ignite the film. But what if something went wrong? What if the film jammed in the gate, even for a second or two? Well, that could be very bad indeed.
If you want to see what a reel of nitrate film looks like when set ablaze, have a look at this video from archivist Geoffrey Rayle:
Now you know why at one time it was illegal to transport motion picture film on any form of public conveyance. The risk was too great. Moreover, once a nitrate film fire is burning, there is essentially no way of putting it out. Turn a hose on it and it will continue to burn. A foam extinguisher can slow it down, but not stop it. I’ve seen video of burning nitrate film continuing to burn after being completely submerged in a bucket of water. If you’re wondering why, remember the chemistry involved. There’s so much oxygen internal to the molecules of nitrocellulose that environmental oxygen is simply not required to support continued combustion. In this scene from Alfred Hitchcock’s SABOTAGE (1936), a young fellow is told by a streetcar conductor that the film he’s carrying is not permitted:
So yeah, there were a lot of movie theater fires. The miraculous thing is that there wasn’t more massive loss of life than there was. A few such disasters occurred, to be sure, like the Paris World’s Fair conflagration of 1897, which claimed 140 lives. But disasters on that scale were comparatively rare in comparison to the high risk involved. This was doubtless due to the extraordinary precautions that were routinely employed to, at minimum, contain any fires to the projection booth. This diagram illustrates some of the common safety measures:
Eventually, however, a less hazardous substitute for nitrate film stock was adopted. An alternative to the nitrate base was the cellulose acetate base, also known as “safety film,” so called because it lacked the volatility of nitrate film. Expose this safety film to heat and instead of bursting into flame it will simply melt. Or if it does catch fire it will burn very slowly, not at all explosively. Cellulose acetate film was manufactured by Kodak as early as 1908, and was the standard film stock for amateur movie gauges like 16mm from their inception (putting nitrate film stock in the hands of amateurs would have been tantamount to manslaughter). But it was only in 1948 that Hollywood studios began transitioning from nitrate stock to safety film. This may seem odd, but the truth is that nitrate film looks significantly better. The blacks and whites are more vibrant, producing strikingly vivid images.
Of course, cellulose acetate safety film is now just about as obsolete as nitrate film since the industry has transitioned to digital imaging. But even nitrate prints have not entirely vanished. Nitrate films are still preserved (carefully, of course) in archives, and now and then it’s even possible to see one projected. Only a handful of projection booths still have the required safety features and the specially trained projectionists, but if you’re willing to travel you can see for yourself what audiences saw on their local theater screens up through the 1940s. The George Eastman Museum in Rochester, New York, hosts an annual “Nitrate Picture Show,” including not only nitrate screenings but also guided tours of the nitrate-safe projection booth. For film history buffs, it’s an enticing opportunity, but I will resist the temptation to call it the hottest ticket in town.