International projectionist (Jan 1941-Dec 1942)

New Treatment for the Prevention of Film Abrasion and Oil Mottle GENERAL film appearance and picture quality have long been major problems with the motion picture industry. Of the numerous factors influencing screen quality, this paper will deal with two, namely, film abrasion and oil mottle. The former of these, film abrasion, has been the object of much research leading to a large number of patented processes, some of which are in use in the trade. These processes, in general, leave something to be desired, either in effectiveness or in price, frequently in both. They depend for their effectiveness on the principle that the treated surfaces will be more resistant to abrasion than those not similarly treated. Whereas this may be true in some cases, the fact remains that no practical film surface has been found which will resist abrasion indefinitely. Therefore, when these treated surfaces become abraded, they present the same problem as do any other scratched films. Protection from Abrasion Experiments have been conducted in this laboratory and in the field with a new type of film treatment based on a new principle. The aim has been to devise a lacquer which can be applied easily and removed easily. This lacquer, when applied to both sides of the film, becomes scratched just as the film surfaces would have been scratched by any sharp points coming in contact with it. If the thickness is correct, however, normal scratches do not go through the lacquer layer into the film. Therefore, on removal and renewal of the lacquer, the film is found to be in as good condition as when new. As for the lacquer itself, it was necessary that it fulfill certain definite requirements. These requirements were: (1) Its manner of application must be simple, requiring practically no special equipment. (2) Its rate of application must be comparable to average processing speeds. (3) It must be easily removable without the aid of solvents or special equipment. (4) It should be applicable to both sides of nitrate and safety films without any deleterious effect upon physical properties, such as curl, flexibility, moisture absorption, etc. tj. Soc. Mot. Pict. Eng. (February, 1941). By R. H. TALBOT EASTMAN KODAK COMPANY (5) It must dry rapidly to give a smooth coating of glossy appearance. The reason why a glossy surface is essential will be discussed later. (6) It should make the films fingerprint-proof. The Eastman Protective Film Lacquer admirably fulfills all the laboratory requirements enumerated. Comparison of coated and uncoated films both immediately after coating and after service in the field has shown that there has been no noticeable change in physical properties. In addition, fingerprints may be removed completely from the coated film by gentle wiping. Films treated with this lacquer will be protected against all ordinary cinch marks and against the normal scratches found on most films which have been in service in the trade. It would be ridiculous, of course, to pretend that any lacquer of a thickness of 0.0001 inch could not be scratched through, if conditions are severe enough. Our experience, however, indicates that such scratches seldom occur in practice. There is one other point in regard to this scratch-protective layer that should be mentioned. It has been pointed out that our aim was to apply a lacquer which would bear the scratches which would normally be found on the film. The question naturally arises, "To what extent does the coating itself become scratched? Does it scratch more or less readily than normal film surfaces?" Protection from Oil Mottle This question can be answered at the present time only in the following way. Laboratory comparisons have indicated that the coated films have approximately the same scratch resistance as untreated films. However, without a single exception, the experience with these coated films in the field has indicated that they are definitely more resistant to abrasion than the uncoated checks. The ultimate answer to this question must be deferred until more practical information has been accumulated. To this point we have been concerned with film abrasion. We will now consider the closely allied subject of oil mottle or, in other words, the continual flicker on the screen due to oil spots on the film. In the course of our study, it soon became apparent that flicker due to oil on the film was more detrimental to screen quality than was the occasional scratch. Scratches which are extremely prominent to the technical people of the industry nearly always go completely unnoticed by the average theatre patron, due, no doubt, to absorbing interest in the story. On the other hand, flicker on the screen must be avoided by all means. Noticed or unnoticed, this mottle most surely has its effect upon the eye and upon the fatigue of the spectator. Although no scientific proofs of this are available, I believe that the comments of the spectators who are allowed to see both clean film and oily film, one after the other, are sufficient indication of the increased pleasure in viewing the mottlefree film. This question of oil on the film has not had the attention given to it which it deserves. Heretofore, it has not been thought of as an actual damage to the film as is the more conspicuous scratch. Furthermore, one has thought that if oil does get on the film it can be removed by cleaning. It is true that oil may be removed easily from a small area of film with a clean pad and fresh carbon tetrachloride, but it is quite another matter to clean an entire roll effectively without streaks, bloom, abrasion marks, etc. Thus it is that oil, which often gets on the film on its initial run, regardless of the quality of the house, usually stays there throughout the life of the film. Large sums of money are spent by film manufacturers, processing laboratories, and studios in order that the photographic quality of the pictures may be maintained at the highest possible level, yet this oil mottle often nullifies completely the careful work which has been done on the picture to this point. The reason why oil spots on film produce mottle is well understood. Each oil spot produces a glossy surface which permits more of the light from this area to be focused on the screen than from the neighboring unoiled surfaces. The remedy, of course, is to make the whole surface glossy so that there will be no more light coming from the oily spots than from the rest of the surfaces. This lacquer accomplishes this to a re(Continued on page 34) JANUARY 1941 17