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Topic: Film Vs "Film"
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 08-14-2003 07:00 AM
In the beginning there was only nitrate, so people didn't really consider advantages and disadvantages. Early in the 20th century Cellulose Diacetate safety film was introduced; it quickly became almost universal for home systems, such as the Pathe KOK 28mm format, introduced in 1912. In this application the highly flamable nitrate film had always been recognised as being undesirable, and was replaced by safety stock as soon as it became available.
The diacetate stock did, however have a number of disadvantages compared to nitrate:
It was more expensive.
It was less tough, and therefore stood up less well to repeated projection.
It was more difficult to cement splice, and a splice was more likely to break during projection.
Due to serious accidents with nitrate film in the early days, most countries introduced strict safety regulations governing its storage, handling and use. In the UK these were contained in the Cinematograph Act of 1909, which came into force in January 1910, and led to the construction of many new, purpose-built cinemas in that year. Similar regulations were introduced in other countries. I don't know if you have ever seen a nitrate projection box, or storage vaults, but if you have you will realise that they took the risks seriously!
These regulations made the use or nitrate film reasonably safe, and this, combined with the disadvantages of diacetate kept nitrate film in general use in professional cinemas.
Triacetate safety stock was intended to overcome the disadvantages of diacetate film, and this it did, to a large extent, unlike diacetate, it was seen as an acceptable replacement for nitrate, which ceased being manufactured fairly soon after thhe introduction of triacetate. It was thought at the time of its introduction that it was chemically more stable than nitrate, but it is now known that under certain conditions of high temperature and humidity it can deteriorate faster than nitrate; the so-called 'vinagar syndrome'. This process can also be accelerated by iron oxide, rust from cans, magnetic striping and storing rolls of 16mm print and magnetic track together in a 35mm can, as was often done with television material, can all cause problems.
Nitrate and triacetate can both survive in good condition for many years, there is material from the earliest days still in good condition, but both can deteriorate rapidly under poor storage conditions. There probably isn't much difference between nitrate and triacetate from this point of view.
Nitrate film contains a plasticiser, often camphor, which is gradually lost in time, causing the film to become more brittle, this happens more quickly at high temperatures. Surviving diacetate also tends to be quite brittle now.
Polyester film has also been around for a long time, but has only recently been widely used for motion picture stocks. Fuji single 8 film was on polyester since its introduction in the '60s. Polyester is much tougher than other bases, and is almost impossible to tear. It has had problems with static, but these seem to have been reduced to a large extent in recent times. It may scratch somewhat more easily than triacetate and nitrate, and it cannot be cement spliced. Polyester film is much more dimensionally stable than other stocks, nitrate, in particular was subject to considerable shrinkage.
Both triacetate and polyester can be magnetic striped, nitrate and diacetate had been replaced by the time magnetic sound was introduced. The oxide in the stripe can cause problems with triacetate, as mentioned earlier, and getting the stripe to adhere to polyseter caused problems in the early days, but improved stripe emulsions were developed for polyester stocks.
Nitrate, diacetate, triacetate and polyester are the most common base materials, but there have been others. There is a post from Leo Enticknap, in response to a question from myself, in a thread entitled 'nitrate film', in this forum which describes the properties of propionate and butyrate film.
A normal cinema is unlikely to see anything other than triacetate and polyester now, but nitrate is by no means extinct. Large amounts of it still exist, and it is handled as an everyday procedure in archives and specialised labs. The British Film Institute alone has about 140 million feet of it in their vaults.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 08-14-2003 10:30 AM
Information about film base:
http://www.kodak.com/US/en/motion/support/h1/base.shtml
Deterioration of cellulose nitrate and cellulose triacetate film is greatly slowed by proper film storage. Cool and dry storage is known to slow the reactions that cause "vinegar syndrome" (hydrolysis of the film base) and dye fading. Vented storage (or sealed storage with Molecular Sieves) helps prevent the buildup of moisture and acid vapors that can accelerate degradation. Periodic inspection of the film by careful rewinding is recommended to look for any degradation, as well as allowing the film to "breathe" and relieve winding stresses:
http://www.kodak.com/US/en/motion/support/technical/storage1.shtml
http://www.kodak.com/US/en/motion/support/technical/vinegar.shtml
http://www.kodak.com/US/en/motion/support/technical/molecular.shtml
http://www.rit.edu/~661www1/sub_pages/8contents.htm
http://www.amianet.org/11_Information/Information.html
http://www.sentex.net/~ritchpat/danchek.html
http://evora.omega.it/~demos/faol/references.htm#
http://www.smpte.org/smpte_store/standards/ (SMPTE RP131 Storage of Motion Picture Film)
Polyester motion picture film was introduced by Dupont in a paper published in the December 1955 SMPTE Journal: "Polyester Photographic Film Base" by White, Gass, Meschter, and Holm, Volume 64, pages 674-678. Kodak licensed the technology, and began producing ESTAR base motion picture materials in the late 1950's, which were widely used for industrial, educational, and special venue (e.g., Disney theme parks,IMAX) theatres. Kodak did NOT recommend the use of polyester prints for 35mm general release prints.
The need to fit more (thinner) film on mini-platters, and the desire to eliminate perforation damage, led NATO and distributors to ask for conversion to polyester print film in the early 1990's. In 1990, NATO's Technical Advancement Committee resolved to "approve and recommend the use of polyester film, which is thinner (allowing more film per reel) and less liable to break" (NATO News and Views, January 1991, page 6).
When polyester print film (mostly from other manufacturers) was first being used for 35mm theatrical features in the early 1990's, many problems were reported, and Kodak warned of the issues of static generation, projection abrasion, and the need for proper equipment design and tension-sensing failsafes. I presented data from an early polyester print release ("Mr. Wonderful") at ShoWest on March 8, 1994, discussing these issues.
During the 1990's Kodak invested over $200 Million in research and development, and capital expenditure for a new base making machine, that led to the development of today's Kodak VISION Color Print Film, which has a proprietary conductive scratch-resistant coating on the ESTAR base, as well as enhanced lubrication, to reduce static charging and provide protection from projector abrasion:
http://www.kodak.com/country/US/en/corp/pressReleases/pr19960509-01.shtml
http://www.kodak.com/country/US/en/motion/newsletters/inCamera/fall98/print.shtml
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