Film-Tech Forum ARCHIVE: Flamable Eastman Saftey Film?

This is topic Flamable Eastman Saftey Film? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mitchell Dvoskin (Member # 751) on 04-11-2001, 04:35 PM:

I have an old Monogram feature, re-printed on 1950 Kodak film stock, clearly marked "safety film" on the edge, that will burn if you put a match to it. The edge code reads EASTMAN (some dots & bars) (TRIANGLE PLUS) SAFETY FILM.

It is clearly not nitrate, it burns slower and not as completely. For example, I took about 10 frames and held them with pliers over the sink, and lit the bottom corner. It burned up to the top, but only on one side of the film. Nitrate would have vaporized almost instantly in the same test. I then put another piece in front of a heat lamp, and it curled and melted without igniting. Again, nitrate would have gone up. It also immediately went out when doused with water, and did not burn when wet.

My question is, I though Safety Film was supposed to only burn as long as you held a flame to it. I was unaware that any safety film would burn, and was wondering how unstable and/or dangerous this stuff was?

Posted by John Pytlak (Member # 331) on 04-11-2001, 04:52 PM:

Cellulose TRIACETATE safety film will burn, much as paper (another cellulose byproduct) will burn. Cellulose NITRATE film is self-oxidizing (can burn without the presence of oxygen), which is why nitrate film is so dangerous.
http://www.kodak.com/US/en/motion/support/faq/combustable.shtml
http://www.kodak.com/US/en/motion/support/faq/autoignite.shtml

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by John Schulien (Member # 215) on 04-11-2001, 05:18 PM:

Cellulose film is chemically similar to magician's flash paper, and has similar burning characteristics.

Burning a small segment of nitrate film will result in a fast-moving flame, but isn't necessarily dangerous, IF the burning is performed away from other flammable materials and the evolved heat is able to dissipate.

For instance, you could unroll 100' of nitrate film down the sidewalk, light one end, and the film would be quickly consumed in a steady, fast-moving, but fairly low-temperature flame. Similarly, if you were to unroll a firecracker, and burn the gunpowder in the open air, you would get a flash, not an explosion.

What IS dangerous is when concentrated nitrate film -- for instance, film on a reel, especially an enclosed reel -- is burned.

Ordinarily, when you burn something, the limiting factor is the availability of oxygen. Close the vent holes on your grill, and the fire will go out, because you've take away the oxygen.

Nitrate film contains its own oxygen, which means that access to oxygen is NOT the factor that limits how fast the film will burn. Instead, the temperature is the limiting factor, and as nitrate film burns, it gives off heat, which causes the film to burn faster, which gives off more heat, which increases the rate of burning. Now, if you've concentrated a lot of film in a very small space ...

Depending on how tightly the film is enclosed, you have duplicated the conditions in either a rocket engine, or a bomb.

Posted by Mitchell Dvoskin (Member # 751) on 04-12-2001, 03:49 PM:

Thank you, John, for the above links, especially the auto ignite link. That was the info I needed. My projector is designed to keep the film gate area cool to the touch. I am not generating nearly enough heat to start a fire even if the film were to break in the gate.

Posted by Randy Stankey (Member # 64) on 04-12-2001, 08:50 PM:

When asked about whether or not safety film will burn, I simply tell people that it is similar to any other kind of plastic when exposed to heat/fire. I know that's not entirely correct but it's enough to get the point across without going into a lot of detail.