Theatre Catalog (1946-47)

large, the moving film may touch projector parts not intended to guide the film, with consequent scratches and abrasions. Short loops may cause any amount of damage to perforations, varying from slight pulling or nicks to outright tearing and irreparable destruction, so the ruined sections of the print must be discarded. A projector sprocket turns at constant speed to drive film into the upper loop, but pull-down claws advance at greater speed as they intermittently move it through the gate. If the upper loop is too short, it will not contain a sufficient length of film to allow unimpeded intermittent film travel through the gate, and then perforations may be pulled or torn. Slack in the loop is taken up and film is pulled taut between the sprocket and the pull-down claws because it is not fed into the loop as fast as claws move in their downward stroke, and since film does not stretch like rubber, it must tear or break. SPLICES Difficuities that may arise from poorly made splices are so well known that they should require little mention. When a bad splice passes through the projector, there is always danger that it will part or that film will break, especially when going over sprockets or through the gate. A splice-should not be thin from too much scraping to remove emulsion, but thick splices also may give trouble, and it is often helpful to scrape the base lightly, in addition to removing the emulsion, to reduce thickness of the splice and give better adhesion. Film cement should be fresh and applied neatly, sufficient for good adhesion but without excess that makes film buckle at the splice. The finished splice should be smooth and clean, for sharp edges at the ends where films are joined, or dirt lodged at the splices before cement is dry, may cause abrasions or scratches, particularly when film is run in a continuous projector. PROJECTOR CHATTER When-film is green or contains excessive moisture, fragments of emulsion may be scraped off and accumulate in the gate. In such cases a projector sometimes runs quietly for a short time and then becomes more noisy. with increasing chatter which may suddenly stop and then gradually return after a few moments of quiet operation. Such an occurrence indicates that dirt or emulsion or both are accumulating in the gate and rubbing against the films with increasing pressure until the film binds against the foreign deposit and dislodges it. A period of relatively quiet operation then follows until another deposit of emulsion or dirt begins to accumulate, WARPED AND BUCKLED FILM A film that is warped or buckled may give trouble as it runs through a projector because the film does not lie flat and will not remain in focus. The uneyen or warped film is subjected to friction and binding as it passes through the 1946-47 THEATRE CATALOG gate of the projector, and because the film does not remain in focus, it may be necessary to increase tension at the gate to hold the film flat. This adds insult to injury, and a vicious circle comes into being as the further increase in tension leads to further excessive Wear and abrasion. Another source of difficulty is the rewinding of film after projection. If rewound too rapidly, it cannot cool properly and take up moisture from the atmosphere to replace that lost from heating during projection. Film may dry out very little during any one run, but wound in a roll, it can take up moisture only at the edges. Therefore, repeated projection with certain machines, followed by rapid rewinding, constitutes a process of slow drying and so the films may finally become quite dry and brittle, possibly accompanied by buckling or waviness when edges of film in a roll take up moisture between projections or during storage. BRITTLENESS AND CURL A film that is too dry from improper storage or repeated projection, without treatment to restore the required moisture between projections, will be brittle and very susceptible to breaking or damage to the perforations. Over-dried film also shows excessive curl, for, as the emulsion coating gives up moisture, it shrinks more rapidly than the base material, thus causing the edges of the film to curl towards the emulsion side. Curled film may require increased tension in the gate to hold it in focus during projection, thus leading to troubles similar to those from warped or buckled film. UNEVEN WINDING Sometimes, instead of winding normally, film assumes a bumpy irregular contour, and in extreme cases a given length of film may wind so unevenly that all of it cannot be held on a reel normally intended for that length of film, unless wound with excessive tension. This angular, uneven winding is simply another manifestation of curl when film contains insufficient moisture. Curl across the width of a film gives it longitudinal rigidity like that of a soda straw or a carpenter’s “flexible” steel rule. Such articles are longitudinally inflexible, and if sufficient force is applied, they do not bend in one long curve but “break” sharply at definite points, separated by straight sections that remain unbent. Curled film behaves the same way, and the cause of angular winding is obvious. PRINT INSPECTION When a film is returned after projection, it should be inspected, cleaned and re-humidified, if inspection indicates such treatment is required. Seriously damaged portions should be removed, or if damage is less severe, but like nicked perforations, the beginning of progressive deterioration, it should be recorded on a suitable card covering the life history of each print. Film inspectors should wear thin white cotton gloves to avoid finger marks on prints. HUMIDIFICATION With repeated use, film loses moisture from heat in projection, and condition of showing, whipping, or storing film may prevent its restoration. Exposed to cool, humid air, dry film takes up moisture and becomes flexible again, but the average library has no facilities for unwinding lengths of film so the entire emulsion surface is exposed to air for humidification. Storage of tightly wound film rolls in a humid atmosphere PROJECTION IS THE MOST IMPORTANT OF FACTORS influencing the service life of 16-mm. prints. While equipment like this Bell and Howell Company Filmosound projector is designed to do its part, projectionists and all film handlers have important parts to play, too. And the film itself plays no small part in enjoying a long life. Considerations of the factors influencing service life—and how to achieve the maximum—are set forth in this article. 571