International projectionist (Jan-Dec 1952)

INSPECTION, SPLICING AND CARE OF FILM (Continued from page 14) lowed. It is important to use fresh cement. Bench bottles should be cleaned out regularly and filled with new cement. Poor splices attributed to the particular brand of cement being used, or the characteristics of the film, may in most cases be explained by lack of attention to details covered in the above paragraphs. Helpful hints on good splicing and splicing faults are given in Figures 13-23. Film Deformation Motion picture film is similar to other plastic materials in that it has certain physical limitations. Distortions can occur through improper storage, through faulty FIGURE 21 Tilted springs FIGURE 22 Cementetched scraping surface FIGURE 23 Dull scraper handling and under very severe projection conditions. The various types of distortion are commonly referred to by exchange inspectors and theater projectionists alike simply as "warping" or "buckling." It may happen that the exchange is at a loss to understand the problems encountered by the projectionist because the description of the condition of the film has been inadequate. Likewise, conditions correctly described would help the laboratory locate the source of the difficulty. A uniform terminology pertaining to different types of film deformation will be of great assistance in locating the causes of such deformation and in eliminating further trouble. Some of the most common forms of deformation are illustrated in Figures 24-27. BUCKLE: This type of distortion may be either temporary or permanent. Temporary buckle results from loss of moisture from the edges of the film when rolls are stored under dry air conditions. Permanent buckle is caused by loss of solvent from the edges of the film when rolls are stored in moist air. EDGEWAVE OR FLUTE: This type of deformation may also be either temporary or permanent. Temporary edgewave or flute may occur along both edges as a result of elongation of the edges relative to the center of the strip during early storage under moist conditions. Permanent edgewave or flute may occur along one edge if the roll is wound under high tension. TWIST: This effect is produced in new prints by loose winding of the film emulsion side in, under dry air conditions. If the film is wound emulsion side out under the same conditions, the undulations do not alternate from one edge to the other as shown in Figure 26, but are directly opposite one another. CURL: This type of deformation is caused by dimensional differences between the emulsion layer and the support. It results from changes in moisture content of the emulsion layer and support with variation in relative humidity. SPOKING: This type of distortion is caused by loose winding of film which has a high degree of curl. Permanent spoking is seen as twist when the film is unwound. Temporary spoking disappears when the film is unwound. EMBOSSING: This is a type of deformation which often occurs when prints are projected with high intensity lamps. The excessive heat causes actual expansion of the picture area, and the frame stands out in relief. This distortion has no detrimental effect on the screen image quality. FIG. 26. Film Twist. An extreme flute or edgewave extending all the way to the center of the film. Waves thus alternate from edge to edge. FIG. 24. Film Buckle. This is the condition that exists when the edges of the film are shorter than its center section. (Opposite of Fig. 25). FIG. 25. Film Flute. Also called Edgewave. Condition that exists when edges are longer than film center section (Opposite of Fig. 24). FIG. 27. F;7m Curl. When one surface is shorter than the other. With emulsion side concave the curl is positive; in reverse case, negative. 28 INTERNATIONAL PROJECTIONIST • June 1952