The Optical Magic Lantern Journal (June 1889)

Transparencies on Gelatine Plates. RANSPARENCIES can be made from any desirable negative at night, using common gas for an illuminant. Having placed the negative in an ordinary printing frame face upwards, proceed (in the dark room) to lay upon it, face downwards, a gelatine plate, then close the frame and expose to a gas flame for a few seconds according to the density of the negative. By farthe most convenient arrangement for this purpose is to have the gas laid on to an ordinary dark-room lamp, and also to a separate bracket for exposing purposes, this latter being fitted with a form of burner recently introduced, by means of which a light may be immediately produced or extinguished at will by simply turning a knob; a small by pass-jet, which is protected, ignites the burner by turning the handle or knob. This indispensable adjunct to the transparency printing room is shown in the cut. For the purpose of exposing transparencies this will be found to be of great value, as it does not necessitate the opening of the dark room lantern. As will be seen, the production of an actinic or nonactinic light is under the control of one hand, the non-actinic lamp being kept burning. After the plate has been exposed it may eitherbe put away while others are being exposed, or developed at once. For this purpose it is laid, face up, in a tray or developing dish; and after being rinsed with water, in order to remove all traces ofa greasy character, developed. “ The most popular and recent form of developer is that in which hydroquinone plays the all Theo Optioal Magio Lantern Journal and Photographio Enlarger. important part. A good formula for this is the following :— A—Hydroquinone u. 15 grains, Cryst. Sulphite of Soda... ... 75» Water 0. 5028. B—-Carbonate of Soda Gure) 90 grains. Water .. . 5028. C—Bromide of Potasstum Distilled Water For use take equal partsof A and B, and if it is necessary to use a restrainer, one or two drops of C; with ‚thig-the plate is flooded, and a slight rocking motign.giventothedish. Ina shortspace of time the-pieture will begin to appear. The development is continued, not only until ail the detail is out, but considerably beyond, or until it has—to a novice—the appearance of being overdone; forit must be remembered that the transparency is for exhibition by transmitted light, and upon the density,to a certain degree, depends the vigour ofthe picture. The necessity for sufhciently developing cannot be too strongly urged upon the znexperienced, as this is the chief point in which one who is making his first attempts is liable to fail. After development the plate is rinsed, and ihen fixed in Hyposulphite of Soda ... ... 2ozs. Water ... ... sie ae RD after which it is thörughiy washed. Itisthen ready to be set aside to dry. It has been claimed that immersion of the plate in methylated spirit produces a greater degree of brilliancy in the high lights; it certainly ensures the plate drying speedily. On the subject of mounting the slide, much depends on the skill and taste of the operator:: but the details respecting this important department will be treated upon subsequently. I 10 or IS per ct. solution. —n PROJECTION.— A magnified image of a picture or of any phenomenon when tthrown upon a screen by means of sunlight and lenses, or with a magic lantern, is called a projection. MOONLIGHT EFFECT.—A charming moonlight effect may be temporarily imparted toa picture by the expedient of inserting with the slide a small square of greenish-blue glass. The same effect may also be produced by interposing such a piece of glass in the rays of light in front of the lantern objective. TırLes on PHOTOGRAPHS.—To write a title on a photograph so that it will appear in white letters,an ink composed of a strong solution of cyanide of potassium, a little iodine, and sufhcient gum arabic to prevent it from spreading. will serve the purpose. re