Journal of the Society of Motion Picture and Television Engineers (1950-1954)

over the film to the exhaust must affect this value as well. Effect of Squeegeeing on Drying Times The majority of this work was done with the squeegee adjusted to a constant pressure of 3 psi. This pressure was selected after a series of experiments showed that this was the minimum pressure which would insure that all the surface-water drops would be removed at the film speeds used. Under these conditions the drying effect of the squeegee varied with the film speed; therefore, the moisture content of the film entering the cabinet was a function of the film speed and was different for each point on a drying curve. In the case of Fine Grain Release Positive, the initial moisture content of the film dropped as much as 3.5% moisture as the film speed was decreased from the maximum to the minimum drying during the determinations of the points on a drying curve. The same amount of change in the initial moisture occurred in determining drying curves of negative films absorbing as much as 45% moisture. The required drying times found in Figs. 5 through 9 were obtained at lower film speeds and therefore at the lower moisture content of the entering film. It would be expected that the required drying times would be greater if the initial film moisture was higher. Investigation of this point showed that the maximum difference in the required drying times was of the order of 10% and this was found only with films absorbing less than 20% moisture, such as Fine Grain Release Positive. Drying curves at constant initial moisture were obtained on Super XX Panchromatic Negative Film, which absorbs 40% moisture, but comparison of these results with those in which the initial moisture varied showed no difference in required drying time. If the performance data of this equipment are used as the basis of design for commercial equipment, it should be assumed that the commercial squeegee would be adjusted for a minimum of drying and therefore the required drying times given for Fine Grain Release Positive should be increased by 10%. The required drying times of the other films are unaffected by this slight change in initial moisture and do not require this correction. Effect on Film Properties In general the physical properties of the films dried under these conditions differed very little from the properties of the same films dried on conventional machines. The author wishes to stress that these remarks apply only to the films actually tested and that it would be a mistake to assume that all films would react similarly. Careful measurements of the brittleness, curl level, humidity curl amplitude and distortion were made on all of the films which were used in the experiments. A comparison of these values with typical values of normally dried film showed no outstanding differences. The films used in the investigation and the measurements made are listed in Table II. In drying the films for these measurements, the machine speed was adjusted so that the film would be dried to approximately a 50% R.H. equilibrium moisture content. In addition, some samples were purposely overdried, particularly at the higher air temperatures in order to show any effects of overdrying. When the films were not overdried, the rapid drying had little effect on either the curl level or the humidity curl amplitudes. In the case of the Fine Grain Release Positive there was some lowering of both of these values. Overdrying did not seriously affect either of these properties, although there is a slight indication that it may lower the humidity curl amplitude of some of the films. The effect on the brittleness, as indicated by the Vise Brittleness and Pfund F. Dana Miller: Rapid Film Drying 99