The motion picture projectionist (Nov 1931-Jan 1933)

November, 1931 Motion Picture Projectionist 17 The Rejuvenation and Preservation of Films By J. A. Norling** and Albert P. RipPENBEiNf This paper briefly describes a method of treating positive and negative motion picture film for eliminating abrasions and scratches and improving its elasticity. There are two treatments: (a) the rejuvenation or regeneration process, by means of which worn and damaged negatives and positives are restored to good condition and (b) the impregnation-preservation process, by means of which new negatives and prints are given a longer life in service or in storage. The processes do not involve the use of lacquers or coatings, but depend upon the swelling and contraction of the film and the glazing of the surface in order to resist scratchiyig and accumulation of surface dirt. A PHOTOGRAPHIC film contains colloidal systems which tend to change as the film ages. This change develops serious symp Fig. 1. Film Cleaning Machine toms: the film shrinks and tends to become dry and brittle. The mechanical strains and stresses to which dry and brittle films are subjected during use soon cause a breakdown of perforations. The nature of the photographic emulsion, and likewise, of the base, makes it a receptive medium for accumulating moisture, oil, and dirt. The substances of which the emulsion is composed are not highly resistant to abrasion and scratches appear in a short time under normal use. These scratches become receptacles for dirt. The dirtier a scratch, the worse it appears when projected. Therefore, when a film becomes scratched during the first run, which may occur on poor equipment or on good equipment improperly operated, subsequent use of the film will make these original scratches more and more apparent. In addition, new scratches will be added constantly, and by the time the print arrives in the smaller theatres, it has acquired the "rainy" appearance which has been a source of much perturbation t o conscientious projectionists throughout the country. Any process that will reduce scratching, wearing, and absorption of dirt will be of great benefit to the industry. Many processes have been used which involve the use of lacquers and varnishes. The Recono processes differ from these in that they do not employ any lacquers or coatings whatever. Two Distinct Treatments These processes for treating film were developed by Frederick J. J. Stock, of Munich. They have been in successful use in Germany for the past eight years, and in this country since the beginning of 1930. They provide two distinct treatments: (a) the rejuvenation or regeneration process, by means of which worn and damaged negatives and positives are restored to good condition; and (6) the impregnation-preservation process,_ by means of which new negatives, blackand-white and color prints, and prints made by the different color processes, are given a longer life in service or in storage. The treatments are similar in the following respects: (1) They are both essentially chemical treatments which effect definite physical and chemical change in the film. (2) Both treatments involve an impregnation of chemicals into the emulsion layers and, in the case of the rejuvenation treatment, into the celluloid as well. The emulsion layers and celluloid are made to swell and are partly liquefied in order to permit them readily to absorb the chemicals required in the process. The Rejuvenation Process By the rejuvenation process, scratches and abrasion marks on both the emulsion and celluloid sides of negatives and positives are almost en tirely removed. Dry, brittle film is restored to an elastic condition, and warped film is straightened. The removal of scratches is effected by causing a temporary swelling of the celluloid and emulsion layers, thus bringing together the walls of the scratches. After the swelling is reduced by drying, the walls of the scratches adhere. Elasticity is restored by impregnating the celluloid with material to take the place of the material that has evaporated. Neither distortion of the film nor disturbance of the relative positions of the silver grains results from this treatment. The impregnation-preservation treatment is applied only to the emulsion side of negatives and positives with the following results: (1) The surface of the emulsion is increased in hardness, making it more resistant to scratching. This advantage is obtained not only without the accompaniment of dryness and brittleness, but with an actual increase in the film's elasticity, amounting to as much as 15 per cent when measured at the breaking point. (2) The emulsion surface is given a high gloss which has a beneficial effect in resisting scratches and accumulation of surface dirt. This gloss makes waxing unnecessary. (3) The emulsion layers are made resistant to the absorption of oil and moisture, and the original moisture content of the emulsion is sealed in. The film therefore tends to retain the moisture necessary for preserving its elasticity and its tendency to resist buckling or warping under excessive heat. (4) Perforation checking and damage are reduced because of the greater permanent elasticity imparted to the film. Two Steps Required The first step in the rejuvenation process is the cleaning of the film. ♦Courtesy of the S. M. P. E. Journal. **Loucks & Norling Studios. fAmerican Recono, Inc. Condition Thickness in Mm. Test No. Per Cent of Elongation at 7.5 10 Breaking Kg./Cm. Kg./Cm. Point Tensile Strength (Breaking Weight in Kg. per Cm. Width) (Average of 15 Tests) Not Treated 0.146 mm. 1 2 3 2.2 1.8 1.8 3.2 3.0 3.0 36 33 28 15.65 14.30 13.95 Average 1.9 3.1 32 14.60 Treated 0.148 mm. 1 2 3 2.0 1.8 2.2 3.4 3.2 3.5 33 37 40 14.35 15.15 16.15 Average 2.0 3.4 37 15.20 Comparisons oi Elongation and Tensile Strength