> > > >

1952 Theatre Catalog, 10th Edition, Page 295 (259)

1952 Theatre Catalog, 10th Edition
1952 Theatre Catalog
1952 Theatre Catalog, 10th Edition, Page 295
Page 295

1952 Theatre Catalog, 10th Edition, Page 295

(see point indicated by arrow in Figure 11) at the intermittent guide holder is not great enough for films with high positive curl. Some projectionists have filed this center section to increase the clearance. This is a satisfactory solution to the problem if it is very carefully done and the surface is polished to satin smoothness after filing. If any file marks remain, however, there is the chance that these can cause even more severe damage than that caused by the holder in its original condition. Another method which has been used successfully by a number of projectionists but which is possible only on certain makes of projectors, is to raise the lower loop slightly by threading over the first pad roller and under the second roller as usual, as illustrated in Figure 12. When this is done, it may be necessary to readjust the rollers in such a way that there is sufficient clearance at the second roller for two thicknesses of film. This alternate threading procedure permits the film to fiow onto the sprocket from the intermittent loop more easily and with less plopping of the loop than is the case when the film is threaded in the conventional manner (Figure 13).

Signalling Devices

Signalling devices contained in the film supply magazine which employ a small ball or roller, which rides on the emulsion side of the film, should be checked frequently for binding or wear.

FIG. 10. Trap door which has been taped to control flutter.


FIG. 12. An alternate method of threading used by some projectionists to elevate the lower loop slightly.

Such devices in poor operating condition could prove harmful, particularly on a new print when the emulsion is most susceptible to damage.

New Print Sticking

While a new print is assumed to be ready for projection, the projectionist might encounter sticking on first runs due to insufficient lubrication of the print. This is commonly referred to as tfgreen printi, trouble. In order that the projectionist may be better advised, it might be well to explain why this sticking occurs, how it affects the film and what steps can be taken to relieve the trouble.

One of the usual ingredients of the emulsion of motion picture film is gelatin ea substance which is hygroscopic and readily gives up or absorbs moisture to reach equilibrium with the prevailing atmosphere. The gelatin in freshly developed emulsion retains a considerable amount of moisture and is readily affected by heat which makes it soft and tacky. The first point at which new film comes in contact with high temperature is at the aperture of the projector. Here the light is concentrated and produces heat to a degree which softens the gelatin and causes it to collect on the tracks or shoes at either side of the aperture 01' at a point slightly above or below this level, as indicated in Figure 14. Here it rapidly dries to a bone-like hardness. As the new film is projected, this hard deposit continues to accumulate and offers further resistance, which may result in deep rub lines, usually along the line of perforations or in the area between the row of perforations and the edge of the film. As this resistance increases, there is the added danger of the teeth of the intermittent sprocket seriously damaging the perforations, sometimes to such an extent that the print is beyond repair.

When print sticking occurs, prompt action is necossmy. Some projectionists apply oil in generous amounts to eliminate the trouble. This is effective but it is unnecessary and undesirable. Such

application covers the picture area of the film where no oil is needed and seriously impairs the quality of the projected image. A very small amount of oil on the thumb and finger, applied at intervals to the perforation area (alternating from one side to the other), before the film enters the trap or gate is all that is needed to work the film through. At the end of the run, the tracks can be cleaned to remove any remaining hardened deposit. This should be done with a damp cloth or if necessary, a copper coinenever with a hard metal such as a screw driver, knife or razor blade. A scraper fashioned from a toothbrush handle, is a handy implement for this purpose. It must be remembered that deposits will form more readily once the

FIG. 11. Intermittent guide holder showing point of narrow clearance.

1952 Theatre Catalog, 10th Edition, Page 295