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May, 1952
drown: problems of storing film
153
new tin ; but the original tin was eaten with rust. It was, I imagine, with something like this in mind, that the B.K.S. Committee recommended the use of containers other than the usual tinned sheet-iron ones. Various circumstances have led us to continue to use such cans; and under the conditions which exist in our vaults, and with constant surveillance, no damage is likely to ensue from this cause. One wonders how many films have been lost through being just put away and forgotten. In one place from which
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Fig. 2.
(a) Side elevation of vault, showing louvred ventilator.
(b) Plan of vault.
the Library obtained some films, one had to walk on duckboards because there was an inch or two of water on the floor. There is no problem here, as far as films which are in our hands are concerned, it is simply a matter of keeping a sound roof over their head.
Ideal Storage Conditions.
Our object therefore must be to provide, as far as possible, the conditions of store in which the inevitable decomposition pro
ceeds most slowly. The conditions which were recommended by the B.K.S. Committee are :
1 A low and steady temperature. For maximum longevity the film should be kept at as low a temperature as possible above actual freezing point. 33° — 40° F. was suggested.
2 A constant relative humidity of 50 per cent.
It is also necessary to permit the escape of decomposition gases. Therefore film cans must not be sealed, and for the same reason it is essential that the reels are not stored on edge ; for the weight of the reel then compresses the lower layers of film together, and the vapours cannot so easily escape. We have had several films which have been stored on edge, in which three or four frames of each of the outside layers have become sticky, while the rest of the firm is in reproducible condition.
The maintenance of a temperature as low as that proposed would require refrigeration, which would be expensive and would lead to problems in handling. It would be impossible for staff to work continuously at such temperature, and it would be necessary to bring films into a warmer room whenever it was required to handle them for any purpose.
To bring films straight out of cold storage into a room at working temperature or to return it to cold storage directly from working temperature, would violate the requirement of steady temperature. Also bringing a cold film into a warm place would lead to a deposition of moisture on the film, which would, of course, be intolerable. Therefore a chamber in which the temperature of films could be raised or lowered over a range of about 30° F. during a period of hours, would be a vital provision under this arrangement. Moreover what would happen to a single reel when brought directly from cold storage, would also happen on a larger scale if warmer air from outside should enter the refrigerated store. The moisture vapour in the air would be condensed on all the surfaces; on the wall of the stores, on the