The Educational screen (c1922-c1956])

Page 10 The Educational Screen Some Common Causes of Damage to Slides and Films PROBABLY the most frequent cause of damage to films is a bent reel. If the lip of the reel is bent inward at one point it is apt to catch the film at each round and tear or cut it along one edge. When one edge of a film is damaged at regular intervals this is very likely the cause. Such damage is irrepairable and can only be rectified by complete replacement. This same damage may be caused by a point being bent out far enough to contact the reel box and thus throw the reel out of plumb which in turn drags the film over the reel edge. Toed-in reels catch the film and put a strain on it. Films may be damaged as easily on a re- wind as on a projector. The rewind units (if they are separate) must be in line, otherwise the film slaps against the reel and may be cut. Films should never be rewound rapidly (the mile-a-minute rewinding causes havoc with film) since there is bound to be some slapping against the reel and consequent damage. Torn or enlarged sprocket holes is another type of damage. This is due to several possible causes. If the holes are torn on both sides it is apparently due to some extra strain, or pull, having been put on the whole film. And this in turn may be caused by letting the loops become too small, or a tension screw to become too tight. If the damage appears only on one side of the film it is perhaps due to either a dirty sprocket tooth or to a hooked tooth. The hooked tooth can only be detected with a microscope. Neither the dirty or hooked sprocket tooth w-ill tear or enlarge every hole on one r.ide of the film, but only those it contacts; hence, the damage will be of recurring kind—every third or fourth hole, for example. Scratches are made on film by bits of hardened emul- sion becoming caked on the edge of the aperture (hole through which the film is shown). These bits of hardened emulsion may be very small, but they cut deeply into the surface of the film. They can be re- moved by lightly scraping with a penny, this being copper is fairly soft metal and will not scratch the metal of the aperture plate. A touch of moisture will help in this operation. Scratches cannot be removed from film, and thus require replacement of the film. The source »f scratches can be traced by the exchange to identical patterns found on two reels from the same school. Blisters are made on film by allowing the film to stand too long before the light. Stop-on-film devices should be used with extreme caution. They are sel- dom of any great use and they certainly do cause much damage to films by thoughtless users. We have known By B. A. AUGHINBAUGH Director of Visual Instruction, State of Ohio, Columbus teachers to put a blister on a reel of film at every new scene. This is pure vandalism. Brittlcness in films may be caused bv lack of mois- ture in the texture or, in cold weather, by low tem- perature. It is well to allow films to remain in a room until they approach room temperatvire before project- ing them. Dryness may be overcome by wrapping the reel in a damp (not wet) cloth and leaving it for a few hours. One objection to circuiting films is the likelihood of their becoming dry from the heat of the projectors and no moisture returned by the use of humidors. We have put sponges in the lids of our shipping cans to overcome this to some extent. These sponges should be kept damp (not wet) by those on the circuit. Misframes (pictures half up and half down) are due to improper patching of films. All splices are made by the exchange with a splicing device, which assures smoothness and accuracy. A splice should never ex- ceed one sprocket hole in width and it should not be made with an excessive amount of cement as this makes it hard and thick. The splice should extend to the very edge of the film, otherwise the film will curl up at that point. Film should never be cemented with any cement but that obtained in a photo supply house .selling motion picture film of the 16 mm or smaller size. All of non-inflammable film, both 35 mm and 16 mm, requires the type of cement mentioned, which is for 16 mm film (and all 16 mm is non-inflammable). Schools using theatrical films as well as non-inflam- mable films are the worst oflfenders in this respect as the boys who are allowed to do the operating do not know the difference in the two kinds of films and think any cement will do. But this is not the case. Careless operators. We debated whether or not to put this cause first. It is said that most auto accidents are due to youthful drivers. It is a characteristic of youth to presume knowledge not possessed, and in this day almost every boy thinks he is a finished mechanic. He probably reaches this conclusion from seeing the unschooled workmen who are willing to pass judgment on any ailment of a motor car that falls into their gar- age clutches. The superintendents, principals, and teachers probably know more about a motion picture projector than these boys, only they have a finer sense of modesty. It is the old story of "fools rushing in", etc. We have yet to see the school boy who could be allowed to take charge of projection work without careful supervision of a teacher. If they do nothing {Concluded on page 31)