R. G. Harris

The object of these chapters is to place before the slide worker a general review of the standard process for the production of slides, with descriptions of reduction and contact methods, and details of such accessories as may be deemed most useful to the general worker. For the benefit of those who have yet to make their preliminary trials in lantern slide work the subject will be treated ab initio, without assuming even an elementary knowledge of the process on the part of the beginner. Later on, processes will be described that appeal more directly to the advanced worker and to the lantern slide enthusiast; processes that are viewed by many simply with historical interest, and yet are capable of giving the finest results when facility in their working has been acquired. Albumen, collodio-bromide, wet collodion are processes that few modern slide makers connect with lantern transparencies, yet for downright quality no modern process can claim superiority over the time honored albumen, and slides- of Ferrier's of thirty years ago hold their own when compared with the best work of today. Wet collodion, in capable hands, is still the process par excellence for obtaining crisp, bright results with a minimum expenditure of time and trouble, and collodio-bromide has the merit of having fixed a standard of excellence for the modern gelatine lantern plate.

A question the beginner in lantern-slide work will most probably ask himself is, " What constitutes a lantern-slide?" He is, most probably, already in possession of the fact that, in the negative he has taken, the lights and shadows of the original are reversed and that to obtain them as they existed in the original it is necessary to get from the negative a print which gives the lights and shadows of the original as they were seen by the eye. This "positive" print on paper will be viewed by "reflected" light, i. e., by light reflected to the eye from its surface. If the gelatine film of a P. O. P. print was stripped from its paper support the "positive" image would be seen to exist in this film, but as there was no longer any white background paper to reflect the light through this image it could not be seen as a positive. Suppose this film was now laid upon a clean piece of glass and pressed firmly and evenly into contact with it, on being held up between the eye and a clear view of the sky the positive appearance would be restored and the picture would again be seen as plainly as when it was supported on the white paper. The film, in fact, has now become a lantern slide, but instead of being made apparent to the eye by light reflected from the white paper support, the eye sees the picture by light transmitted through the film from the background of the sky. It will be obvious, then, that fundamentally there is no difference between the paper print and the lantern slide, but that the one is, for convenience, placed upon a white paper support while the necessity for using transmitted light in the optical lantern demands that for a lantern slide the image bearing film be borne upon a transparent support.

It follows from what has been said that lantern slides can be printed from the negative in just the same way as an ordinary silver print, provided that the same sensitive material is used upon glass instead of upon paper; the image could afterwards be toned and fixed as though it were a paper print. At one time, considerable lantern slide work was done in this manner, as the image becoming visible during printing, offered facilities for modifying it not available when the image required developing. The inconvenience of using an inflexible support in the printing frame, which prevents a ready view being obtained of the depth of the print, coupled with the slowness of the process, debarred it from attaining any permanent popularity. At the present time lantern slides are produced almost exclusively on the lantern plates of commerce.

The exposure of a lantern plate may be either by "contact" or by" reduction." Suppose the worker employes a quarter plate hand camera for taking the negatives, he can make his lantern slides by placing the negatives in the printing frame as used for paper, adjusting his lantern plate upon the negative, film to film, closing the frame and exposing to gas light for the necessary time. In this case he is working by "contact" and as the size of a lantern is 3 1/4" x 4", while the quarter plate is 4 1/4" x 3 1/4" it follows that, when working by "contact" some portion of the original negative has to be omitted.

It is frequently the case that when working from hand camera negatives some portion of the original negative can be omitted without detracting from the value of the picture, but where larger sized plates are used, half plates and upwards, contact printing is out of the question unless some very small portion of the original is desired. When it is desirable to make lantern slides from negatives which are of much greater dimensions than the lantern plate the slides are got by reducing the original size of the negative, by means of the camera, until it shows on the focussing screen the same size as the lantern plate. A lantern plate being placed in the dark slide and exposed to this image will result in a lantern slide that embraces the whole of the subject that is in the larger negative. This constitutes the method of work known as " reduction." Later on full description of these two methods of working will be given, with the apparatus necessary in each case.

Some workers of experience contend that finer results are got when making slides by reduction, even in the case of quarter plate negatives. I am inclined to think that such is the case, though the gain in quality is not sufficiently striking to impress a beginner.

One decided advantage camera reduction has over contact printing is that, should any uneveri-ness be present in the surface of either negative or lantern plate, the definition is not impaired. " Contact" printing is certainly the simplest form of exposure for the beginner, and as it can be conducted without any special apparatus, as it is entirely independent of daylight and with some lantern plates, even of the customary dark room, it is the method that will receive the first consideration in these chapters.

Before commencing any description of the methods whereby lantern slides are made, it may be well to caution the beginner against depriving himself of sufficient light in the dark room. The sensitiveness of lantern plates is so greatly inferior to that of plates used for negatives that it will take the beginner in lantern slide work some time before he acquires the courage to use all the the light permissible with these slow plates. Some lantern plates are so slow that they can be manipulated in the light of a naked bat's wing burner, if it be turned down, and the plates are not exposed unnecessarily to its light. With the ordinary lantern plate, made for reduction and contact work, the light of a para-fine lamp screened by two thicknesses of canary medium will give a light that is both safe and comfortable. It is convenient to have between the fabric and the lamp burner a sheet of finely ground glass which affords a very pleasant diffused light whereby to judge the density of the slide. It is convenient also, on taking the slide from the fixing bath to raise the cherry colored fabric and have the greyed surface to examine the slide by.

The negative for contact printing, which will probably be of quarter plate size can be placed in a quarter plate frame such as is used for paper printing; it is carefully dusted with a broad camel hair brush to remove anything that might injure the film of the lantern plate. This latter is then placed upon the negative, the film of the lantern plate against the film of the negative. The lantern plate should not be slid into position over the surface of the negative or damage to the film may result; it should be placed deftly into the position it has to occupy without any need of readjustment when laid down. The back of the frame should be placed in position and fastened by the springs. It must be remembered that the thickness of the lantern plate will cause considerable pressure if the felt pad used in paper printing is employed here also, and usually quite enough pressure to insure contact will be got without using the pads.

Having fixed the lantern plate in the frame it now requires exposing to light. Daylight is practically out of the question, as in spite of the relative slowness of these plates, they are still sufficiently rapid to make daylight exposures unmanageable. The most convenient light is a gas burner, and if it has a bypass, exposures can be readily made in the dark room without loss of time. We must bear in mind the fact that in lantern slide work long exposures give warm colored slides (the developer being suitably adjusted) and short exposures black tones. Suppose five seconds' exposure at a given distance from a bat's wing burner gives a lantern slide of black tone, then with half a minute's exposure at the same distance the slide will have a brown color, and with a minute's exposure the color will be decidedly red. The developer would require modifying in each case to suit the increased exposure. Producing satisfactory warm tones in lantern slides, at the same time retaining other desirable qualities, demands more experience than making a slide having a black color, and such being the case, the beginner is recommended to adhere to the production of black colored slides until he can make them with ease and certainity.

A negative of medium density, held about eighteen inches from a bat's wing burner would require an exposure of some six seconds for black colors, when the ordinary lantern plate was used, and developed with the formula given below :