Photographic Printing may be Done Rapidly by the Systematic Use of This Machine
Nail cleats along the inside of each side of the box, placing them vertical and parallel, and about ³⁄₄ in. apart, so as to form a slide groove in conjunction with the slot. This groove is to receive a frame or curtain constructed of stock, 2 in. wide and ¹⁄₂ in. thick. The outside dimensions of the curtain are a trifle smaller than the inside measurements of the box itself. Cover the frame with orange paper, and when finished insert it through the slot in the top of the box. Build a frame as indicated, on the outside of the box. Along the inside of the uprights fasten cleats, thick enough to come flush with the ends of the slot. These serve to steady the curtain when raised. Make a suitable baseboard and secure the box to it. Then with sheet tin construct a lamp house extending from the back of the box and of sufficient size to accommodate a round-wick lamp. Leave an opening in the top to admit the chimney, provide holes for ventilation, and a door by which the lamp may be adjusted. When completed, paint the interior of the box and lamp house white, to intensify the printing quality of the light. Tie a piece of stout cord to a screw eye inserted in the upper end of the sliding curtain, lead it through two pulleys fastened as shown, and down to the hand lever. The latter is pivoted at the rear end by a bolt. Attach a spring to the lower end of the hinged pad on the printing frame. This holds the pad out of the way when not in use. A curtain-roller spring is suitable for this purpose.
To operate the machine, place the negative and paper in position, and, with the left hand, bring the pad down. Pull down the hand lever with the right hand, raising the orange curtain. When the required exposure is made, release the lever, shutting off the direct light. While nearly all light is shut out by means of the lamp house, the paper may be handled safely and easily by means of that admitted through the orange curtain. By systematic arrangement and handling of materials, it is surprising what an amount of work can be turned out by the aid of this machine, especially if one person attends to the exposing and another to the developing.
A Small Variable Condenser
Diagram for a Small Variable Condenser
The condenser shown in the diagram combines the large capacity of a fixed condenser with the gradual capacity variation of a variable one. It is suitable for a wireless receiving circuit, or to shunt around the vibrator of an induction coil, by making the units considerably larger. It is made up of several fixed condensers, connected in parallel, a lever being the means whereby the capacity is varied. Five or more units may be used, each being a small condenser, built up of 10 sheets of waxed paper and nine sheets of tin foil. A convenient size for the tin foil is 6 by 4 in., and for the paper, 5¹⁄₂ by 4¹⁄₂ in. The latter should be a good grade of very thin linen paper and should be carefully prepared by dipping it in hot paraffin. The sheets of tin foil and paper in each unit are piled up alternately, allowing about ¹⁄₂ in. on each tin-foil strip to project beyond the paper for making connections. The pile is covered with heavy paper, and a heated flatiron is passed on the top of each unit until the paraffin begins to melt. Upon cooling, the units are compact.
The connections necessary are shown in the diagram. The condenser units C, D, E, F, G, each have one side connected to a common terminal A. The other sides of the condensers are connected to the copper strips H, J, K, L, M. They are ¹⁄₂ in. wide and ¹⁄₁₆ in. thick. A copper lever, ¹⁄₈ by ¹⁄₂ by 8 in., is pivoted on one end so that it will connect two or more of the condensers in parallel. The pivoted end is connected to the terminal B. The dotted line shows different positions of the lever. The apparatus is mounted in a wooden box.—Peter J. M. Clute, Schenectady, N. Y.