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Topic: Kodak Film Stock Question
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 02-02-2005 04:40 AM
Agreed - triacetate burns with roughly the same intensity as paper. However, this print could still be nitrate. This is a well-known issue with elements produced around the time of the conversion (the danger zone is roughly 1948-55).
Remember - a safety internegative can be (and was) printed onto nitrate release print stock, and vice-versa. It's not uncommon to find both a 'safety' and a 'nitrate' edge mark on the same element. The Hollywood studios and most US and British labs went over to triacetate for b/w camera and intermediate stock almost as soon as it became widely available in winter 1948/spring 1949, whereas for release printing the conversion took a lot longer. There were a number of reasons for this. For example, existing inventories of stock needed to be used up and there were teething troubles at the projection booth end, notably the fact that acetate splicing needed a different formulation of cement from nitrate splicing. It wasn't until February 1950 that Kodak announced that they were stopping the manufacture of nitrate print stock completely, and of course the stuff remained in circulation for a lot longer.
As a general rule, if the edge marking on a print is opaque against a clear background, that means it is original or from an earlier generation interpositive. If it is clear against an opaque stripe (sometimes quite a faint one), it has been printed on from an earlier generation of negative (usually an intermediate but sometimes the camera original). If step printing has been involved along duplication chain, one or more sets of edge markings will not have been copied. Incidentally, that's why archivists will create preservation dupes by continuous contact printing if at all possible: that way you preserve the edge marking information, which can be very useful to have (e.g. date code, stock manufacturer, batch identification).
The upshot is that it's very possible to have a safety release print from the late '40s/early '50s in which the only visible edge mark says 'nitrate' and vice-versa. The only way to be safe is to check. Personally I find that nitrate has a distinctive 'musty' or 'mothball' smell which is virtally impossible to miss, but I guess it might not be so obvious for people who don't handle nitrate very often.
Michael: I can't see anything wrong with the burn test if it's just done on a little bit of spacing from either end of the reel. The only caveat is to be sure that the spacing is of the same stock as the element being tested, i.e. it hasn't been spliced on or is something different. The only other reliable nitrate test I know of is the 'float test', which involves taking a punching of film and placing it in a test tube containing trichloroethylene. As nitrate has a higher specific gravity than this stuff, if it's nitrate it'll sink. If it's any sort of acetate, it'll float. The burning test, however, avoids the need for potentially dangerous chemicals.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 02-02-2005 05:34 AM
Here is Kodak's publication about nitrate film:
http://www.kodak.com/global/en/corp/environment/kes/pubs/pdfs/H182.pdf
Even though the black edgeprint says "Safety Film", I would still verify through testing, as it was in the transition time. Also, until recently, Kodak put a dye in triacetate film base that would glow under ultraviolet light, to aid in identification. By illuminating the roll with ultraviolet light in a darkened room, you could see if there was a mix of nitrate and safety film in the same roll.
A triangle and plus date code could be 1950:
http://www.kodak.com/country/US/en/motion/support/h1/identificationP.shtml#135427
quote:
Until 1982, the date code was comprised of two symbols except for the following years: 1916, a circle; 1917, a square; 1918, a triangle; and 1929, a plus sign. For 1928 and 1948, three circles were used to identify the year of manufacture.
Date codes were repeated every twenty years until 1982. For example, the same symbols appear on film manufactured in 1921, 1941, 1961 and 1981. In 1982, a third symbol was added allowing for many more years of unique date coding.
The other markings are likely slitter and strip number codes.
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Mitchell Dvoskin
Phenomenal Film Handler
Posts: 1869
From: West Milford, NJ, USA
Registered: Jan 2001
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posted 02-02-2005 07:45 AM
Thanks John, I'll check it out with an ultraviolet light tonight. It is definately 1950 vintage.
Brad, it did not go up like flash paper, as nitrate tends to, but it did burn completly like old dried out paper (thanks Leo) leaving nothing but ash.
Michael, no picture or sound frames were burned, just a section of countdown leader that had sufficient sprocket damage that it needed to be removed anyway.
Leo, the print is marked "NITRATE" in white (clear) letters on one side, and "SAFTEY FILM" in black letters on the other. Being that this was originally an 1943 release, I am assuming that the white nitrate is a print thru from the negative.
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Bruce Hansen
Jedi Master Film Handler
Posts: 847
From: Stone Mountain, GA, USA
Registered: Dec 1999
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posted 02-04-2005 06:47 PM
The dangerous thing about nitrate is that it generates it's own oxygen as it burns. Acetate will burn, but if the fire hits the roll of film, in most cases, the fire will go out, because it cannot get enough oxygen to keep burning. If a fire reaches a roll of nitrate, RUN. If you have some "junk" nitrate, take about 10 feet of it, and roll it up into a small roll. Light it, and stand back. I did this one time, a three foot flame shot out of the roll, and it sounded like a rocket taking off.
I tried burning a short strip of both types of film, and there was not much difference in the way the strips burned. It was just when a roll of film is involved that there is a BIG difference.
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