The Educational screen (c1922-c1956])

March, 1925 The Use of Visual Aids in Teaching 149 no danger of fire, but yet the laws must be lived up to, much inconvenience and harm as they work. It is only another example of how inadequately laws keep pace with progress, proving that it is a pretty safe assertion, one industry with another, to say that law is at least twenty-five years behind invention." We are permitted in New Jersey to use a portable machine of a certain type in schools without the machine having to be enclosed in a fireproof booth either with inflammable or non-flam film. This in my judgment, is a progressive step and will be productive of a large use of film for instructional purposes. Every school auditorium seating 400 or more should be provided with a booth where a standard professional machine may be housed, but for class-room use schools should be permitted to use portable and semi-portable machines without the enclosing fireproof booth. Non-Flam — versus — Inflamable Film There is a movement on foot to have all film for instructional purposes printed on non-flam stock. Those who have had experience in handling film will agree with me, I think, when I state that non-flam film, up to the present time, is very much more difficult to use than the inflamm.able. It dries out more easily and is more difficult to patch successfully, however, there has been an improvement made in this stock during the last two years. Directions for the Care and Use of Film 1. The standard width motion picture film is a strip of celluloid 1% inches wide by about 6/1000 inches in thickness. There are sixteen pictures to a foot of film and each picture is one inch wide and % inch high. There are four sprocket holes on both sides (if a single picture. There are two kinds of positive film, inflammable (nitrate cellulose) and non-inflammable (acetate cellulose.) The inflammable film burns quickly but is not explosive. The non-flam film burns slowly and is being used more and more for nontheatrical purposes. It dries more quickly than the inflammable film and its wearing qualities is about 80% of the inflammable. 2. Film should be kept in air-tight containers supplied with moistening fluid when not in use, to prevent becoming dry. 3. More harm is done to film through careless threading than from any other source. Be sure that the sprocket teeth are meshed with perforations on both sides of film and that the loops are ample before starting the projector. Be sure that the film is in good physical condition before it is run. 4. Inspection of a film consists of running it from one reel to another on a regular rewinder, allowing the film to pass through the hand so that the thumb and fore-finger are pressed against it sufficiently to cup it. This is done to detect poor patches and torn sprocket holes. Patches begin to loosen at the corners, and often embarrassing stops can be avoided by using a little cement in these places when inspecting the film. Torn sprocket holes should be notched and as a rule when two or more successive sprocket holes are torn this portion of the film should be cut out. 5. To make a patch, cut the film leaving a stub the length of one sprocket hole on one side. (By stub is meant a part of the next picture.) On the other side cut exactly on the dividing line between two pictures. When doing this, it is convenient to have the emulsion side up. Moisten slightly that portion of film over the frame line and remove the emulsion by scraping. Be sure that the emulsion around sprocket holes is removed cleanly and only up to frame line. Apply cement evenly to part where emulsion has been removed and quickly press other end of film to this so that sprocket holes line up perfectly with enough pressure for the cement to set. Do not use too much cement and wipe (Continued on page 157)