Society of Motion Picture Engineers : incorporation and by-laws (1927)

Lubrication of Film — Crabtree and Ives 527 the latter. It was possible to adjust the pressure on the burnishing roller by means of adjustable screws. With undeveloped film an appreciable degree of burnishing was observed to take place, but with film fixed in a hardening bath the effect was very slight. Moreover, in view of the slight buckling of the film around the perforations, it was necessary to exert considerable pressure on the burnishing roller in order to flatten out the film Fig. 8. Film burnishing machine. SO as to insure perfect contact. As a result of this pressure, a considerable amount of heat was developed, so much so that after the passage of a few feet of film, the gelatin coating commenced to grind away and particles of gelatin accumulated on the burnishing roller, stopping the machine. In order to prevent this it was necessary to apply a thin film of grease or oil to the burnishing roller which reduced the friction and prevented the grinding away of the gelatin. In order to determine the precise effect of the burnishing apart from the effect of the grease, a roll of film burnished with the aid of automobile grease was passed through the projector, and a similar roll was merely treated along the edges with the grease. Since no difference was observed between the projection life of the two films, it was concluded that a mere application of oil or grease was just as effective as burnishing. Experiments were made also with a heat burnisher consisting of a highly burnished roller working above a second roller and between which the film was passed with the gelatin surface in contact with the burnished metal. If the roller was heated to a temperature at which