Documentary News Letter (1940)

DOCUMENTARY NEWS LETTER DECEMBER 1940 17 THE CARE OF FILMS By RUPERT LEE, of Recono Ltd. (Denham Laboratories) "AGAINST A DISTANT backgTound of junglc the rains fall, heavy, dull and vertical. The white man is shouldering his burden. In the palm-thatched huts it is raining. One knew this palm thatching was not water-tight." "The white man is returning to London to marry the leading lady who hasn't changed in fifteen years. Not even her clothes. It is raining in London. The white Georgian doorway of Aunt Agatha's house is half obscured by heavy rain — but no : not in the drawing room — ^but yes! in Aunt Agatha's drawing room, dark, heavy, vertical rain. . . ." The principal trouble with films is scratches and emulsion scratches are, as a rule, the first which appear. After a time, celluloid scratches will appear, and at any time perforations may tear and films may even break. Before making any suggestions as to how films may be fortified against damage, or cured when damaged, it is necessary to impress on film users the importance of projection. The projectionist should make his job an art. A large number of scratches would be saved by a more frequent cleaning of the gate. All films are not the same thickness. Where the tension is adjustable it should be used. Only sufficient tension is required to keep the film steady, and any more is dangerous. Films can be dusted oftener with advantage. Hand re-winding through a silk velvet is a safeguard against dust and dirt. If you find you are getting a persistent scratch always in one place, don't blame the laboratories for supplying films that scratch in one place. The fault may be in the take-up box or there may be a burr on the gate. FORTIFYEVG NEW PRINTS Nevertheless, however careful one is, accidents do happen and a considerable amount of thought has been given to the fortifying of films against too early damage. The idea which occurred reasonably to photographic people was to harden the emulsion. Formalin, alum, formaldehyde, and other substances, have been used, mostly combined with the fixing bath. Some of these are definitely helpful to the emulsion though they incline to aff'ect the celluloid— especially in the case of an acetate base. Another idea was to put a protecting coat over the emulsion. The objection to this was that it formed a sandwich of soft emulsion between the celluloid and the protective coating. There was a tendency — far too frequent — for the coating to come off", and bring the emulsion with it. Waxing does to some extent protect a film against slight surface scratches which often, owing to the wax, become worse as there is a tendency for the emulsion surface to turn over and become ploughed in. Lubrication has been tried. Used in sufficient quantities to make the film very dirty, it is said to be eff'ective. Lubrication is probably not the solution. That a surface is slippery does not necessarily mean that it resists scratches. Skates will cut into ice although they slip very adroitly. The solution lies rather in toughening the emulsion to resist the scratch. My own experiments have been towards using a toughening, on the lines of a coating, but which could be sunk deeply into the emulsion with which it became completely homogeneous. It has been found possible to achieve by this means an improved adhesion to the celluloid base, and by adding to this "impregnating" solution certain softening agents advantageous to the preservation of the flexibility of the celluloid, a double purpose is served. It is possible by proper impregnation of a film from the emulsion side, not only to fortify the picture against scratches, but also to prolong the life of the celluloid. There is one type of film which cannot be treated in this way. Dufaycolour, owing to the colour reseau and the varnish which protects it, is vulnerable to most solutions should they penetrate these. The answer so far is to treat the celluloid from the back. This treatment has been found to improve the flexibility of new films and to improve the adhesion of the emulsion to the base. RESTORING SCRATCHED AND OLD COPIES The cure of emulsion scratches has largely benefited from a proper study of the possibilities of impregnation. Scratches on a film appear on the screen either as black — or less usually, as white. When the scratch shows as white it is because the emulsion has been completely gouged away. When the scratch shows black it is generally assumed to be due to a furrow in either the emulsion or the celluloid which has become filled with dirt, dust, or oil. This is not entirely true. A careful cleaning of the film will not eliminate the black scratch, the persistance of which is owing to the refraction of light on the walls of the trench. Now the nearest solution would be to fill the scratch with something — but something having the nearest refractive index to the emulsion or celluloid. There is a further consideration. The filling would have to be homogeneous with the gelatine layer and celluloid, otherwise, as I have already said in reference to coating and impregnation, there is a danger of detachment. Globe polish has been tried, with a certain mild success on slight emulsion scratches. I cannot find the refractive index of Globe polish, it is not in Molesworth, but it has been a minor success — or so I am given to understand. Coating will eliminate scratches on the emulsion, but this is open to the same objections as I have already mentioned. The solution of the problem is to soften the emulsion sufficiently to allow the colloids used to enter into contract (sic. not contact) with the emulsion in such a way that the whole becomes homogeneous. The scratches disappear and the emulsion is fortified against further damage. The treatment of celluloid has hardly received the proper attention it deserves. To dissolve the surface and press it against a glass roller certainly removes some scratches, but the result is not very astonishing, and takes no account of the quality of the material. Celluloid, like the human body, is composed of certain concomitants and water. (It is perhaps for this reason that some people suppose that a damp pad enclosed in a film canister prevents a celluloid film from becoming brittle.) But it is not the loss of water which deteriorates a celluloid film. Many other substances are lost with age, and as scratched celluloid is generally a slightly elderly celluloid, it is necessary to treat it for scratches and age as well. The question becomes, almost entirely, one of solvents : to dissolve, to soften and to leave a sufficiency of the softening agents so as to achieve a rebirth and to regenerate and recreate the celluloid base as new. Now it is well known that when metals are mixed to form alloys, the results are not an averaging out of the qualities of the elements in the mixture. A mixture of bismuth, lead, tin, and cadmium, all of which alone have a melting point of many degrees, will form a humour-giving alloy, known as Rose's metal, which melts at the temperature of a nice cup of tea. Solvents will show similar freak properties. Certain solvents mixed in certain proportions will give results that can hardly be forecast by a study of the individual characteristics of the various concomitants. It has been found possible to work out graded formulae to suit the age and amount of damage to the celluloid. The process of restoring a celluloid film and removing the scratches is, then, to soften the film to a sufficient depth, to produce sufficient surface tension to restore the gloss, and finally to leave, unevaporated, a proportion of softening agents to assure the original elasticity and plasticity of the film. Today it is possible to fortify a copy before it has been put into service, and often, successfully to restore it again when it has become scratched and old. The cost of either process is very small when compared with the cost of a new copy. With proper care and handling, and correct treatment when any trouble occurs, a film can be made, not only to last longer, but to give, while in service, the clear, steady picture which enables the audience to forget the technicians.