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This topic comprises 2 pages: 1 2
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Author
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Topic: nitrate film
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 05-13-2003 06:41 AM
Pre-1950 almost always means nitrate, but only in the case of 35mm (all elements) and 28mm negatives. Apart from in the USSR and China, where small quantities of 16mm nitrate were used, any smaller gauge is almost always acetate of some description. You do find the odd 35mm diacetate and propionate element, though, especially in the case of things like adverts and trailers, which were printed on safety because they could be sent through the normal post, which more than offset the increased stock price. As ads and trailers were only shown for a short time, the inferior stock durability of early acetates wasn't an issue.
Tread carefully with edge marks, though. It's not uncommon in elements produced around the time of the changeover to see both 'nitrate' and 'safety' edge markings. This is because a nitrate interneg can be printed onto acetate release print stock and vice-versa. As a general rule black writing on a transparent background is your print, and transparent writing on a black (or opaque) background is from a previous generation of negative.
If in any doubt, the burning test is the only really conclusive test that doesn't need any special chemicals. Snip a frame or two of spacing off from the end and ignite. If it burns slowly and evenly, like paper, the chances are it's acetate. If it goes up very rapidly, it's nitrate.
Some early nitrate (i.e. pre-1920s) was treated with fire-retardant coatings which can confuse things in a burning test, but for anything with a soundtrack on it, this test is pretty much 100% reliable.
Suggested reading: Roger Smither & Catherine Surowiec (eds.), This Film is Dangerous: A Celebration of Nitrate Film (2002) published by the International Federation of Film Archives. The book is distributed by Plymbridge in the UK and this is all any bookshop needs to know to order it. Elsewhere it can be ordered direct through FIAF's website, price 60 Euros plus shipping. It's not cheap, but with 690 pages of original and newly commissioned articles all about nitrate, it's well worth it.
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 05-13-2003 04:32 PM
Just to back up what Duncan said: make sure you examine the entire element closely, not just a randomly selected foot or two. Acetate head leaders can be joined to nitrate picture elements: indeed, the National Film and Television Archive deliberately do this for their nitrate release prints shown at the National Film Theatre, so that when the print is at the really vulnerable stage of ramping up to speed through the leader (and thus most likely to generate sparks), it's non-flammable film that is running through the projector mechanism. So whenever you see a cement or tape join, check the stock mark and consistency of the film before and after it.
After a while you get an instinctive feel for what nitrate, diacetate, propionate, butyrate and triacetate feels, smells and looks like. This does need a fair bit of experience, but the way you get that is to note down or remember interesting details about old or unusual film elements as you look at them.
From a safety point of view the bottom line is to be very suspicious and on your guard if the element you're examining is late '40s or early '50s, because that is where you're most likely to come across weird stuff, confusing evidence on the film itself (e.g. multiple edge markings from different generations) or the result of someone having done something stupid.
Edit: sorry, this post seems to be appearing twice but I just edited it to correct a few typos...
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 05-14-2003 04:43 AM
Leo wrote,
quote:
After a while you get an instinctive feel for what nitrate, diacetate, propionate, butyrate and triacetate feels, smells and looks like. This does need a fair bit of experience, but the way you get that is to note down or remember interesting details about old or unusual film elements as you look at them.
Polyester feels completely different, and I can usually recognise nitrate, diacetate and triacetate, though some specimins can be difficult to identify, but I don't know about propionate and butyrate, I've heard of both of them, but that's all. When were they used, how common were they, and what are their characteristics?
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 05-14-2003 07:13 AM
Butyrate looks and feels a lot like diacetate. It was made by using butyric rather than acetic acid to dissolve the cellulose. The decomposition process involves it going very brittle indeed, and is known as 'rancid butter syndrome' due to its characteristic - and needless to say, very unpleasant - smell. When freshly manufactured, it was slightly stronger than diacetate, and the small number of 35mm safety elements from the 20s and 30s tend to be butyrate.
Propionate is another mixed ester stock, introduced by Kodak in 1938 and which was manufactured until 'high acetyl' triacetate superseded it in 1948. It was designed to address the extreme fragility of the diacetate base Kodak used for 16mm at the time. It was a lot more durable, but nowhere near as strong as nitrate. Very little 35mm propionate seems to have been made. The stuff is pretty thick, and nowhere near as prone to shrinkage and buckling as a pre-1937 16mm element. It tends to be less vinegary, too - if you have a film which really stinks, it's unlikely to be propionate.
There are quite a few articles in the Roger Smither book I mentioned above which are either about early or mixed ester acetates, or which mention them (including one by yours truly - pp. 202-12 - a shameless plug, admittedly ![[Smile]](smile.gif) ).
Brian - no bonfires necessary if your films are '60s and '70s. Unless someone had taken a 1960s interneg and printed it onto raw nitrate print stock which had been sitting around for two decades there's no way they can be anything except triacetate.
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Duncan Smith
Film Handler
Posts: 50
From: England
Registered: Jan 2003
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posted 05-15-2003 04:16 PM
Hi Leo,
this is the 2nd reply I've made to your meassages tonite but I thought you'd be interested to know this. You certainly seem to have an encyclopaedic knowledge of film so I am not going to embarrass myself by getting into that but you mentioned the practises of the NFT earlier. I used to work there, during which time we had a week-long nitrate festival. All 35mm, b/w and colour, very interesting indeed. Anyway, the cinemas 1 and 2 were licensed to run nitrate but were not permanently set up for it, so out of these festivas it is not run there anymore. When the festival approached we seet up the old spool boxes on the vic 8's and tested the fire extinguishers on every projector. This was very loud as they went off. Old gun cotton was replaced for new and the CO2 canisters refilled and safety checked ready. It was very well organised and the festival passed without incident. We did however all see a short traingin film made by the navy decades ago showing a reel of nitrate being burned, even under water it still burned, very dramatic!
Referring to your point though, it was never my experience that nitrate films had an acetate leader, quite the opposite in fact to avoid mis-identification. Almost all the films in the festival had original leaders and were left untouched. We had to be especially careful not to open the dowser until at full speed to avoid burn ing the frame out or worse. And definitely no checking the racking on lace up by opening the dowser a bit (which I never do anyway). After the festival the mechs were returned to their normal state for running medern stock etc and have not been used for nitrate since to my knowledge ( about 2/3 years ago).
Of course I don't know about the NFA archive practices as these prints came from other sources I believe.
Hope that was mildly interesting for you anyway.
All the best, Duncan.
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 05-16-2003 03:12 AM
quote:
We did however all see a short traingin film made by the navy decades ago showing a reel of nitrate being burned, even under water it still burned, very dramatic!
That would have been This Film is Dangerous, made by the Royal Navy in (I think) 1943 or 44 as a training film for sailors projecting nitrate films on ships. It is (or was, in my time) shown as part of the induction for all new BFI South Bank and Berkhamsted staff. The fact that they used nitrate at all in a confined space such as ships struck me as a bit silly, but I suppose given that they also had several hundred tons of bombs, ammunition and other dangerous stuff it wasn't much of a big deal.
quote:
...it was never my experience that nitrate films had an acetate leader, quite the opposite in fact to avoid mis-identification. Almost all the films in the festival had original leaders and were left untouched.
All the nitrate films I handled there (late '80s/early '90s) had safety head leaders put on them by the NFTVA before we ever got them. At that point NFT2 routinely showed nitrate and had the spool boxes but NFT1 didn't. As well as all the precautions you mention, the prints were also checked with a 'shrinkometer' gauge.
Most of the work I did was in MOMI in which, needless to say, the idea of showing nitrate would have been suicide (that big glass window - not heat-resistant, as far as I know - for one thing, and the fact that the spool boxes on the DP-70s formed an airtight seal - just what you need for those expanding gases from a nitrate fire).
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 05-16-2003 05:43 AM
Leo wrote:
quote:
That would have been This Film is Dangerous, made by the Royal Navy in (I think) 1943 or 44 as a training film for sailors projecting nitrate films on ships. It is (or was, in my time) shown as part of the induction for all new BFI South Bank and Berkhamsted staff. The fact that they used nitrate at all in a confined space such as ships struck me as a bit silly, but I suppose given that they also had several hundred tons of bombs, ammunition and other dangerous stuff it wasn't much of a big deal.
Most of the projectors shown in 'This Film is Dangerous' are GBN portables, some tungsten lamps, some with arcs, but near the end of the film there is a statement that while this film has concentrated on naval installations, the same principles apply to handling nitrate film in commercial cinemas, or words to that effect, at this point there is a very brief shot of a brand new pair of elephant foot style Kalee 21s. I don't know the location, but even if they were photographed at the Kalee works, I think the film must be slightly later. If I remember correctly, the first 21s were sold in 1947, so I doubt if even prototypes were available until 1946, or so. Unless of course the film was re-edited, and this scene was a later addition, possibly added for the benefit of men leaving the navy to work in cinemas after the war.
I wish I could get hold of a print of that film, on either 16 or 35mm. I always look out for it at collectors' fairs etc., but I've never seen it. I doubt that many prints were ever made of it.
Then he wrote:
quote:
All the nitrate films I handled there (late '80s/early '90s) had safety head leaders put on them by the NFTVA before we ever got them. At that point NFT2 routinely showed nitrate and had the spool boxes but NFT1 didn't. As well as all the precautions you mention, the prints were also checked with a 'shrinkometer' gauge.
I believe the spoolboxes were removed from NFT1 when SR-D was installed, but I don't know the date, they remained in NFT2 for a while longer, but, again, I don't know when they were removed.
On an open day, when Charles Beddow was still there, we were shown a rather odd arrangement in NFT1, they had a rack which held a pair of 2000 foot 35mm boxes, which fitted inside the 6000 foot 70mm ones on the Vic. 8s. I've never seen anything like this elsewhere, was this system still in use when you were there? I seem to remember that the gas system was normally isolated by a clip on top of the bottles, and was only activated when nitrate was being run. Obviously, they don't run any on open days.
Finally he wrote:
quote:
Most of the work I did was in MOMI in which, needless to say, the idea of showing nitrate would have been suicide (that big glass window - not heat-resistant, as far as I know - for one thing, and the fact that the spool boxes on the DP-70s formed an airtight seal - just what you need for those expanding gases from a nitrate fire).
The large window in MOMI was rather similar to the original Telekinema, I never saw it, I was -6 years old at the time, but I have seen pictures. The Festival of Britain films were all safety prints, but the place certainly ran Nitrate when it became the first National Film Theatre, until the present one was built. I assume that this window was bricked up, but I wonder what they did about the exit from the box, it could not have been via a public area.
There has been very little nitrate run at the NFT for years; I have heard conflicting reports as to whether they even still have a licence.
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