Film Conservation
Silver film is a perishable medium and our audiovisual heritage is in danger.
For a lot of works of art the history of cinema is merely a huge obituary announcement where we don't even know the names of all the victims seeing that we ignore the extent of the losses. These are linked to a number of factors including, to start with, a film industry that hasn't necessarily known or wanted to preserve films considered to be "outdated" from a sales value point of view. Sometimes aesthetic or historic judgements on old films don't help with preserving films either towards as they generate little curiosity (like the corporate film for example).
For a lot of works of art the history of cinema is merely a huge obituary announcement where we don't even know the names of all the victims seeing that we ignore the extent of the losses. These are linked to a number of factors including, to start with, a film industry that hasn't necessarily known or wanted to preserve films considered to be "outdated" from a sales value point of view. Sometimes aesthetic or historic judgements on old films don't help with preserving films either towards as they generate little curiosity (like the corporate film for example).
 Le Cauchemar, Georges Méliès, 1896
Decomposed film
A great many films have disappeared since the origins of cinema and it is estimated that 50% of all films before 1950 are missing. The best known example is certainly the filmography of Georges Méliès, where out of more than 500 films made in 16 years (between 1896 and 1912) only 40% (in other words approximately 200) have been saved in 2008. As an image recording technique the film is initially a medium damaged every time it is handled and "mechanical reasons" (problems with splicing, scratches, damaged perforations etc.) are among the primary damage factors. But the main cause is its chemical instability. The film medium is made up of a transparent material on top of which there is a layer of emulsion (we sometimes talk of "gelatine") which is the film's image. Due to their chemical fragility the medium like the image are likely to deteriorate over time. Faced with this parameter a film's shelf life is closely connected with storage conditions for the most part, particularly hygrometry and temperature conditions. |
Perishable media
Until now there have been three main physico-chemical types of silver film medium: the nitrate medium, the acetate medium and finally the polyester medium.
The first invented by Hannibal Goodwin in 1887, is cellulose nitrate also called the "flame film".
The nitrate medium caused a number of problems regarding both its preservation as well as its operational use until the 35 mm format was officially withdrawn around 1953. It is highly dangerous to handle due to one of its components, "nitrocellulose" which is also an ingredient for explosives like TNT (Trinitrotoluene). It inevitably decomposes: first of all it becomes brittle, then the emulsion becomes brown and the film shrinks which can create major problems for contact copying it (in other words making a copy). It becomes dry, sticky and brittle then in the end it ends up as powder.
Until now there have been three main physico-chemical types of silver film medium: the nitrate medium, the acetate medium and finally the polyester medium.
The first invented by Hannibal Goodwin in 1887, is cellulose nitrate also called the "flame film".
The nitrate medium caused a number of problems regarding both its preservation as well as its operational use until the 35 mm format was officially withdrawn around 1953. It is highly dangerous to handle due to one of its components, "nitrocellulose" which is also an ingredient for explosives like TNT (Trinitrotoluene). It inevitably decomposes: first of all it becomes brittle, then the emulsion becomes brown and the film shrinks which can create major problems for contact copying it (in other words making a copy). It becomes dry, sticky and brittle then in the end it ends up as powder.
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However we still find today the very first films made out of nitrate that are still in quite good condition, even though it is claimed that nitrate film is only kept for 50 years "on average". In a certain number of countries including France, a huge plan to transfer nitrate films to another medium, polyester, has been carried out. |
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From 1953 film in 35 mm format (like substandard formats of previous decades) went over to an acetate medium (cellulose diacetate until 1957 and consequently cellulose triacetate). Although it presented no danger when handled, (hence its description of "Safety*"), this medium unfortunately develops a syndrome called "vinegar" if it is poorly preserved. The process starts with a gradual rise in the film's acidity level then speeds up to a point known as "autocatalytic" that ends up in its quick destruction.
For a long time the existence of the "vinegar" syndrome was ignored or underestimated while it is the medium archive cinemas around the world use the most.
Finally a third and last medium is used: the polyester medium. Although invented in 1945, it took some time to be used on a massive scale. After being used for amateur films then for internegatives and advertising films the polyester medium has been used for all copies since the middle of the 1990's.
Although imperfect and today rivalled by digital, polyester is the main medium used by the cinematographic industry but if it is preserved in the right conditions it is the most sustainable medium currently known for preserving films in the long term (there's talk of the medium being preserved between 500 and 1000 years).
For a long time the existence of the "vinegar" syndrome was ignored or underestimated while it is the medium archive cinemas around the world use the most.
Finally a third and last medium is used: the polyester medium. Although invented in 1945, it took some time to be used on a massive scale. After being used for amateur films then for internegatives and advertising films the polyester medium has been used for all copies since the middle of the 1990's.
Although imperfect and today rivalled by digital, polyester is the main medium used by the cinematographic industry but if it is preserved in the right conditions it is the most sustainable medium currently known for preserving films in the long term (there's talk of the medium being preserved between 500 and 1000 years).
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In fact there are no other media at present that guarantee with certainty long term preservation for the archive centre community. Currently all films even those that are 100% digital with a great resolution require a "return" to 35 mm polyester film (even if this isn't necessarily done due to economic reasons). Furthermore, whatever its medium a film can be the victim of a biological attack (like mushrooms) or an external chemical attack (pollution, dust etc.) that can attack the medium itself or the image, hence the need to protect the film from these threats. |
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A fragile image
Parameters linked to techniques for manufacturing the image emulsion are of great importance because some technologies provide better durability than others.
Parameters linked to techniques for manufacturing the image emulsion are of great importance because some technologies provide better durability than others.
A number of techniques and types of emulsions have existed since the beginning of cinema, particular concerning colour film (Read the article The invention of cinema in colour), with copies hand coloured (image by image) since 1897 until the latest fine grain emulsions that have recently appeared. Note that the black and white film or let's call it "monochrome" (even if tinted) has a chemistry that is a lot less complex than colour and therefore doesn't cause too many preservation problems.
 Farfale, 1907,
Hand-coloured |
 Croisière en Méditerranée,
1950, Kodachrome |
 La Grande Revue Philips,
1938, Technicolor |
 Anatole à la Tour de Nesle,
1947, Agfacolor |
From 1928 colour film technologies called chromogenic (whose colours appear during development) monopack in other words film in a single element like the Kodacolor then the famous Kodachrome for example (which preserves well) existed. But these techniques in reversal film (when the film is its own negative that is developed) were intended primarily for amateurs.
The three colour "Technicolor n°4" procedure was developed by Dr. Kalmus from 1932. He used a revolutionary manufacturing procedure leading to very good image preservation in the long term.
The film was made up of three monochrome strips (up until 1954 for the exposure) and an edition technique for copies called by imbibition (technique that existed in the United States until 1974 and even 1993 in China). This system was quite similar to the offset four-colour process by combining black with three layers of superposed colours, whose "inks" are very stable over time. The elements kept separate allow negatives and printed copies to be preserved in the long term, the latter being themselves being very stable over time.
It was necessary to wait for the "Neue Agfa-color" procedure developed by Dr Fischer in Germany in 1939 to see a procedure allowing several copies to be developed from a single film ("monopack"). This technology was the basis of all modern films until today. Unfortunately the colours changed little by little over a few years. A long time after the film is manufactured chemical processes linked to products present in the emulsion from the start continue to act (for example when copies were poorly cleaning when printed), leading to a slow deterioration of the colours and generally a "toning" of copies to red (by the loss of the other colorants).
It seems that copies made between 1960 and 1975 were particularly concerned but in fact even the most recent copy imperceptibly tones from the day it is made. This deterioration is also sometimes responsible for optical faults (clarity, contrast etc.).
It was necessary to wait for the "Neue Agfa-color" procedure developed by Dr Fischer in Germany in 1939 to see a procedure allowing several copies to be developed from a single film ("monopack"). This technology was the basis of all modern films until today. Unfortunately the colours changed little by little over a few years. A long time after the film is manufactured chemical processes linked to products present in the emulsion from the start continue to act (for example when copies were poorly cleaning when printed), leading to a slow deterioration of the colours and generally a "toning" of copies to red (by the loss of the other colorants).
It seems that copies made between 1960 and 1975 were particularly concerned but in fact even the most recent copy imperceptibly tones from the day it is made. This deterioration is also sometimes responsible for optical faults (clarity, contrast etc.).
Storing in adapted places
Ideal temperature and hygrometry conditions involve storing in a cold, dry place. You ideally need a temperature between 3 and 8 °C for colour even if 11°C seems sufficient for black and white. Swiss archives show that at 20% of humidity and 4°C copies would last 800 years and at a minimum you need to respect more or less 50% (+/-10%) and even ideally 30/40% of hygrometry.
Cooling down large volumes of storage at 3°C is of course very expensive and few archive centres can permit themselves to do this financially, even though it is indisputable that considerable progress has been made in the past few years in a lot of archive centres.
