Restoration

Irretrievably Ruined: valuable negatives on nitrocellulose-based film

In the course of a routine inspection of our archive of negatives, we discovered a group of around 160 historically valuable nitrocellulose negatives dated 1930-1941. These large-sized photographs (13x18 sheet film) are primarily pictures of art and architecture in northern Germany, particularly in Schleswig-Holstein. Those showing lost or destroyed works are especially valuable, such as that of the Baroque residential house at Königstraße 44 in Lübeck, with its very lovely Baroque portal (142.923 = mi01960d04, see attachment). Researchers would also be quite interested in photos showing furnishings which have since changed, as in churches, for instance, or documenting the state of preservation of individual objects at that time, such as altars or pulpits.

Of these negatives, 95 were so severely damaged that the original pictorial information had been totally, or nearly totally, lost. It was possible to make duplicates of 67 of the negatives which had only suffered minor damage.

Dangers Arising From Nitrocellulose Film

Since the early 1970's, Foto Marburg has been systematically documenting and restoring its inventory of negatives. This includes not only negatives with a film support made of glass, acetate or polyester, but also nitrocellulose material.

Nitrocellulose negatives were manufactured and used between roughly 1890 and 1960. This material slowly destroys itself chemically, and sooner or later reaches a critical point at which the hitherto imperceptible decomposition begins to accelerate appreciably. This process sets free nitrous gases which can have a damaging effect on other film material nearby! Nitrocellulose film in the early stages of decomposition gives off a sharp, penetrating odor, which is even stronger in the advanced stages, and is also a health hazard! Inhaling the gases must be avoided, and the films should only be touched with protective gloves.

Corroded shelf under a box of nitrocellulose film in an advanced stage of decomposition.
Nitrocellulose negatives which still appear to be in good condition after being competently stored for fifty, seventy or eighty years can completely decompose within ten years! It is not as yet possible to made a prediction in this regard, so that only regular inspections of an archive's inventories can provide information on the state of the negatives or slides.

Especially Critical Types of Film

Of the various nitrocellulose negatives stored in our archive, a large number fortunately still outwardly appear to be in good condition. However, we have noticed that a certain type of this material has changed dramatically or completely self-destructed since the last inspection ten years ago. These are 13-by-18-cm black-and-white negative films with "Eastman Kodak 45" on the exposure and a prominent triangular notch on the upper edge of the picture. The same applies to serial numbers 31, 44, 64 and 122. Sheet films marked "14 Kodak" on the exposure and featuring three triangular notches were likewise ruined.

These sample photographs show how dramatic the effects of this decomposition can be. The nitrous gases have even damaged the shelves right through the film boxes, and neighboring negatives have been badly affected, as well. At an inspection in 1996, the nitrocellulose material still appeared to be in good condition to the naked eye, while advanced decomposition was observable in 2006.

Causes and Remedies

Such rapid destruction is not alone the fault of the film material, but is also exacerbated by improper storage: the damaged or ruined negatives were in sealed polyethylene envelopes. The material itself does not release any toxins, but rather is too dense to allow air to flow through, as do glassine envelopes, for example. If the negative boxes are furthermore densely packed, then the nitrocellulose negatives "stew in their own juice" and the damage accelerates. On the other hand, these envelopes do not entirely protect neighboring film material, although better than glassine envelopes.

In principle, nitrocellulose film should be separated from the other inventories.

Cool storage (8° - 12° C) at a relative humidity of 40 – 45 % is recommended. However, to avoid unpleasant surprises, nitrocellulose inventories should be duplicated and professionally disposed of. This may not stop the decomposition process, but at least it will slow it down. Once they are ruined, negatives cannot be restored, thus leading to an irretrievable loss of valuable pictorial documents.

More information on this topic:
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