MAKING LANTERN SLIDES.
I first commenced the practice of photography the number of amateurs who made their own lantern slides might almost be counted upon the fingers of one hand. Since then photographic operations have been almost revolutionised, and, owing to the substitution of gelatine for collodion, and the introduction of commercial dry plates specially prepared for the purpose, nearly every amateur photographer nowadays tries to make his own lantern slides. Nor can anything be said against the practice, for although at first the results may not be equal to those pro duced by professional slide-makers, yet the very fact of their being the worker's own production at once gives them a value which the best commercial slides would necessarily lack.
English lantern slides measure 34 by 34 in., and plates of that size, coated with emulsions prepared specially for transparency work, can be obtained from any dealer ; for nearly all the well-known plate makers also make and sell lantern plates. I cannot undertake to recommend particular brands ; I have used, at one time and another, every known make, and the general quality is so good that I believe it is possible to obtain, with a little practice, equally good results upon any of them. The beginner should select one particular make, and stick to it until he is able to produce a passable slide.
There are two ways of making lantern slides, namely, by contact printing, and by reducing in the camera. I shall, however, here only deal with the former method of working.
There are two kinds of gelatine lantern plates made, some being coated with bromide of silver emulsion, and others with chloride of silver emulsion. The former are considerably quicker than the latter, but for contact print ing this is no particular advantage, and therefore I re commend the novice to make his first experiments in lantern slide making on chloride plates. A box of these, therefore, should be procured. The plates being very slow, are not nearly so easily affected by exposure to light, therefore plenty of illumination can be used ; indeed, the one thickness of the yellow fabric recommended for bromide printing will be found to afford a perfectly safe light. Upon opening the packet the novice will probably have some difficulty in determining which is the coated side of the glass, the emulsion being of • an exceedingly transparent character.
If, however, the finger nail be cautiously rubbed on the extreme corner of the plate, the coated side will be detected immediately, or the tip of the finger may be moistened, when the tacky nature of the gelatinous surface will be at once revealed. The negative from which the slide is to be made is placed in an ordinary printing frame, one of the lantern plates carefully superimposed, and the back of the frame closed. This leads one to refer to the single dis advantage of making lantern slides by contact, namely, that if the negatives be of larger dimensions than the slide, the whole of the composition cannot be included. It is better, therefore, when the negatives are produced with the special object of obtaining from them lantern slides by contact, to make them on quarter-plates. At the same time, it is often possible to pick out portions of larger negatives which will give good results. Care must be taken, however, when the negative is larger than the slide, in placing the lantern plate in position, to avoid scratching the surface of the negative.
We now come to the question of exposure, and for this particular work artificial light has many advantages. The source of light may be a gas or lamp flame, but magnesium ribbon will be better than either. By observing the pre cautions recommended for securing uniformity in results laid down in the chapter upon bromide printing, as to keeping the source of light at a fixed distance from the printing frame, uniform results upon chloride plates can be easily secured. When the correct exposure for a particular negative has been ascertained a note of it should be kept. As the plates of different manufacturers necessarily vary somewhat in rapidity, it is useless to specify any particular exposure ; but as a rough guide about 3 in of mag nesium ribbon, burnt at a distance of 15 in from the negative should give, with a negative of good printing quality, a proper exposed slide ; dense negatives, of course, will require more, and thin ones, less exposure. The strip of magnesium ribbon, it is, perpaps, unnecessary to say, should not be held in the fingers, but nipped with a pair of ordinary pliers ; the quantity used should be measured and not guessed.