American cinematographer (Sept 1933)

176 American Cinematographer © September 1933 At top is illustrated the Correx Developing Kit, which is more fully described in this article. At bottom is the spiral reel type of developing-rack. Equipping the Home 16mm. Laboratory by WiSliam StuEl, A.S.C. E QUIPMENT needed for the home laboratory for the development and printing of 16 mm. film is not elab- orate. All of it can be purchased and some of it made if the experimenter desires. You’ll need something to hold the film, which can be either rack, drum or reel. You’ll need a tank to develop, a drum to dry the film and a printer to print it-—-and there you are. Pin-racks are probably the oldest type of developing- rack; they consist simply of a cross-shaped or X-shaped frame, with uniformly-spaced vertical pins extending up from the arms of the cross so that the film is held with its edge at right angles to the surface of the solution, and completely immersed. Such racks can, of course, be made and in any size needed. A rack twenty inches square, made of two strips of wood or brass, 20 inches long by '/ 2 -inch wide by '/ 4 -inch thick, joined together in cross-shape, with 34 rows of pins made of one-inch lengths of '/s-inch dowel-stock, spaced '/s-inch apart ,and with a clear space 3 inches in diameter in the center (to allow for a handle), will hold slightly over 100 feet of film. By making the rack X-shaped rather than cross-shaped, you can easily de- velop a 100-foot roll of film in any ordinary 18x24-inch tray. Such a rack is probably the cheapest equipment one can get; but like many other cheap articles, it suffers from serious disadvantages. In the first place, the action of the developer will not be even; you will get uneven streaks across the film wherever it is in contact with one of the pins, producing a light flash at regular intervals in the finished print, known as “rack flashes’’ to the professional. Also, you will find that the fairly abrupt bends at these same places give the negative a semi-permanent wrinkle or irregularity, which usually impairs the print. Frame racks are, as the name implies, simply rectangular frames—sometimes fitted with guiding pegs—about which the film is wrapped, and which are, in turn, placed in deep, narrow tanks, for development. Up to a few years ago, such racks were used very extensively in developing pro- fessional film, but they have been almost universally dis- placed by machine development now. At least one professional laboratory uses the drum sys- tem, and a smaller type of drum is commercially available, I believe, for amateur use: this method certainly is the most economical in the small amount of solution needed (all that is necessary is enough to wet the lower face of the revolving drum)—but the equipment needed is com- paratively bulky, and extremely difficult to operate safely in total darkness, as must be done when using Panchro- matic or SuperSensitive films. The principle of the Stinemann rack is simple: merely a metal spiral into which the film is threaded (emulsion-side out, of course), and the ends of the film clipped in place with ordinary paper-clips. The film is kept on the rack through the developing, fixing and washing operations, and then removed to a drying-drum. The Correx System is essentially similar, except that the spiral guide is flexible, and is wound on the reel together with the film. If you have used the Correx equipment for developing “Leica” film—or even the old “Kodak roll-film developing tank,” you will be able to visualize the working of this reel-and-apron system. The Correx equipment con- sists of a pair of wire reels, a corrugated-celluloid apron of the proper length, a wire flange, and a loading-frame. In use, the apron is wound around one reel, and placed on one spindle of the loading-frame, while an empty reel is placed on the other. The apron (which has about a yard at each end which is not corrugated) is started onto the empty reel; then the film, which has been placed on a third spin- dle, is fed in with the apron before the corrugated portion starts to unwind, thereby holding the film securely in place. At this point, or before, the wire flange is placed on top of the reel being filled, so that the film and apron will wind straight and evenly, and the two are wound together onto the reel. When this is finished, the outer end of the apron is clipped, the upper flange is removed, and the reel, with the apron and film wound upon it, is transferred to the developer, which is in one of the round tanks supplied with the outfit. It is not wise to attempt to dry the film on the develop- ing-rack (and, of course, impossible when using the Correx system). Therefore, a drying-drum should be built. This is simply a wooden drum of appropriate size, with open, ribbed faces rather than a solid circumference, and mounted horizontally so that it can revolve freely. The film is wound around this drum (emulsion side out), and held in place at each end by rubber bands wrapped around one of the ribs and clipped onto the film: this allows for the con- siderable contraction which the film undergoes in drying, which would otherwise either break the film or unfasten (Continued on Page 190)