Fig. 5—Developing Long Films
A reel should be prepared for drying the film. This can be made of small slats placed around two disks to form a drum (Fig. 6) about 1-1/2 ft. in diameter and 2-1/2 ft. long. After the film has been passed through the various solutions and is ready for drying, it is wound spirally around on the slats with the gelatine side out, and the whole hung up to dry.
Fig. 6—Drying Reel
Printing
The printing to make the transparency is accomplished by a very simple arrangement. The negative and positive films must be drawn through a space admitting light while their gelatine surfaces are in close contact. A box may be constructed in several ways, but the one shown in Fig. 7 illustrates the necessary parts and their relative positions.
Fig. 7—Printing Machine
The sprocket A is placed directly back of the opening B which may be regulated to admit the proper light. The sprocket can be purchased from a moving-picture stock house cheaply, but if the builder so desires, one can be made from wood turned up about 1 in. in diameter, or so that the circumference will receive sprockets at points 3/16 in. apart. The sprockets are made of metal pins driven into the wood. Two rows of them are placed around the wood cylinder about 1-1/8 in. apart.
The cylinder is provided with a small metal shaft at each end which turns in round holes or bearings in the sides of the box. One of the shafts should project through the side of the box and have a grooved wheel, C, attached. The sprocket cylinder is driven by a smaller grooved wheel or pulley, D, to which a crank is attached for turning. The relative sizes of these wheels are determined by the speed of the exposure and the kind of light used. A 3-in. or 4-in. wheel on the cylinder sprocket shaft, driven by a pulley about 1 in. in diameter, will be suitable under ordinary circumstances. The opening B may be adjusted by two metal slides which fit tightly in metal grooves fastened to the wood front. The metal grooves and slides can be made of tin and painted a dead black. The films after passing over the sprocket, fall into the bottom of the box, or, if very long films are to be made, the instrument can be used in the dark room and the light admitted only to the opening B, then the ends can be dropped into a basket or other receptacle at the bottom and the unprinted portions carried on reels above the box.