Movie Makers (Jan-Dec 1930)

rE^Mtiiy^Be^* 1930 PRACTICAL DEVELOPMENT A Continuation Of The Discussion Of Home Laboratory Work THE actual practice of photographic development is a very simple procedure if a few pieces of apparatus are available. Of course, the most important of these are the tanks and racks. There are four types of tanks and racks adapted to motion picture development. These are the ordinary, deep tank, the drum rack and tray, the pin-cross rack and tray and the spiral rack and round trays. The deep tank is a square, narrow tank, usually of wood, which is filled with developing solution. The rack is made of wood in the form of a square which will just fit into the tank. The film is wound spirally around this rack and immersed in the solution. Deep tanks are usually used only in professional laboratory work. The drum rack and tray is simply a large cylinder of wood or other convenient material around which the film is wound. A shallow tray is so arranged that the drum may be lowered to a position where the film will be immersed in the solution in the tray at the lower part of the drum as it is revolved. This type of developing equipment has found favor among the amateurs of Europe but not in this country. The pin-cross rack consists of two bars of wood fastened at right angles to each other. Non-corrosive metal pins are set in these arms. The film is wound around these pins which serve both to separate and support the loops of film. A square, shallow tank or tray is made to fit the rack. When the film is wound upon the rack, it is merely set in the tray, care being taken to see that there is sufficient solution in the tray to entirely cover the film. Possibly the most popular form of developing equipment for amateur use is the spiral rack. This consists of a ribbon of metal wound in a continuous open spiral and held in this position 86 By Herbert C. McKay by braces on the bottom. Round tanks are provided into which the rack fits comfortably. Such a rack is easily filled by suspending it upon a rewind and rapidly revolving it while feeding the film into the spiral. Racks and tanks of this type are compact in relation to their film capacity and the resulting development leaves nothing to be desired. In addition to the actual racks and tanks, the amateur technician will need the usual sundries such as a pair of balances for weighing chemicals, one or two glass graduates, a safelight, thermometer, stirring rods, absorbent cotton, etc. The chemicals necessary to start are metol, hydroquinone, sodium carbonate, sodium sulphite, potassium bromide, potassium metabisulphite, potassium permanganate, borax, glycin, caustic soda, citric acid, hypo, common alum and acetic acid. Preparation. The first requisite for successful developing is the proper kind of place in which to work. This should be a room which, while lighttight, may be readily and fully ventilated. As many amateurs will use either the kitchen or bathroom for this work, the problem of ventilation is quite simple, as the short time during which the room will be closed will not seriously interfere with comfort. Provision must be made in the room for hanging the safelight in a position which will provide adequate illumination, yet which will not give any possibility of fogging the film while working. The table should be provided with a rewind or other supporting pin in case spiral racks are used. It is essential that such provision be made if the racks are to be loaded speedily and accurately. The trays should be placed upon a level table in proper order — developer, rinse, hypo. When the equipment has been placed for the most convenient working conditions, the actual solutions may be prepared. Mixing Chemicals. Mixing chemical solutions is not simple in the sense that it may be done carelessly but it is very easy if directions are followed and the most elementary precautions taken. In the first place, one must remember that various systems of weights and measures are used in compounding photographic solutions. Those most commonly used are apothecaries', avoirdupois and metric. Most formulae published in this country are based upon the avoirdupois system. Certainly the metric system is the most logical and sensible, but the difficulties of converting the proportions from the avoirdupois to the metric system prevent its wide adoption. Occasionally formulae will be given in "parts." For example, a given solution may be indicated as being used in the strength of one to ten. This may be regarded as a mixture of one part of the original solution and nine parts of water, or it may be regarded as a mixture of one part of the original solution and ten parts of water. Fortunately, photographic solutions act in such a manner that the slight error involved in interchanging these methods of mixing parts will not seriously interfere with the results. Of course, more careful chemists use the expression, "to one part of solution add nine parts of water," or whatever the degree of dilution may happen to be. In the actual process of mixing, one rule should always be observed, that is, to mix chemicals in the order given in the formula. There are certain formulae originating in Continental Europe in which this order is not observed. However, English and American formulae are prepared in this manner. The reason for doing this is that certain chemicals are very difficult to dissolve in water but dissolve readily in solutions of other chemicals. For example, hydroquinone dissolves far more readily in a solution of sodium sulphite than in pure water. Another excellent practice is to make sure that each chemical is thoroughly dissolved before adding the next one. Any formula will be found to give the expected results provided the chemicals are carefully compounded and ordinary care and cleanliness are observed in the process of mixing. The developing and fixing baths are both to be prepared and the solutions placed in the tanks before the room