R. G. HARRIS

At the present time nearly the whole of the lantern slides produced by the vast army of lantern slide workers are made on commercial lantern plates. Their convenience and excellence have won for them an impregnable position in public favor, which is not yet without justification. The colors obtained upon the ordinary commercial plate range from an admirable black through browns to red, and even purple, should anyone have a taste for claret colored-lantern slides. The classification of colors obtainable on on a gelatine plate has been extended ad nauseam, and is often merely an individual statement of accidental results, the "rich sepia " of one man being the "warm brown " of another, the ingenuity shown in framing formulae to obtain these results having served to encumber the pages of photographic literature with a mass of recipes utterly bewildering to the uninitiated. The colors most generally useful are black, warm black, brown and warm brown.

To obtain any of these colors with certainity and to repeat the exact color obtained upon one occasion at any subsequent time is not easy, and the slide maker will find that he is forced more or less to compromise by accepting considerable departures from any standard color. Each worker, therefore, must adjust the developer to his own personal equation and method of working. The formula given in this chapter will be found to give the color described with tolerable exactitude, but as the worker in lantern slide operations progresses he will most certainly modify any formula that comes into his hands to suit his own requirements.

Before proceeding to a detailed account of the development of gelatine lantern plates, it may be well to mention that color in lantern slide work, more especially when made on gelatine plates, is almost entirely a matter of exposure followed by suitably adjusted development. Any reducing agent, hydrokinone, metol, eikonogen, etc. will give either warm or black colored slides if modified to suit the exposure. Short exposures in a strong light, followed by quick development, tend to the production of black colors, while long exposures, coupled with protracted development, result in colors more or less red. If therefore, the beginner bears this in mind, he will be able to make a rational application of any developer. In connection with this point, it may be interesting to give the results of some experiments made by H. Liesegang, and published in the Photograqyic Cyronik.

Although these results were derived from a series of experiments on the development of silver chloride, they agree very closely with what the lantern slide worker finds to be the case with gelatine lantern plates, which, in fact, are largely composed of silver chloride. The production of black colors in lantern slides calls for no special skill on the part of the worker; so long as he uses a clean, quick working developer and gives a short exposure, the rest is easy. In camera reduction, when working for black colors the light outside, if daylight methods are used, must be sufficiently good to give a well exposed plate with six to ten seconds exposure, and when "contact" exposures are made, the illuminant is better fitted for the production of black colors if it takes the form of an incandescent gas mantel. With such a light, and a negative of medium density held at a distance of about eighteen inches from it, the exposure need not exceed ten seconds. Any of the modern reducing agents will give black colors, but each one has a particular shade of black peculiar to itself. Thus, hydroquinone gives a black that often assumes a greenish hue, especially with caustic alkalies; metol is characterized by its bluish black; and eikonogen has a very pleasing olive black. Amidol, in my opinion, gives the nearest approach to a pure black of any developer, though it is run very close by Edinol.

It will be seen from a consideration of the above peculiarities what a considerable undertaking it would be to give formula embracing all the recently introduced developers, with their varying shades of colors. I shall content myself with giving here several simple formulas, which are the sublimated results of many month's experiment among modern developers. Once the lan-slide worker has passed through his apprenticeship, he will find the field of modern developers extensive enough to afford him many months' work, and the result will be sufficiently varied to suit the most exacting.

Amidol Developer (For Black.)

Development is very rapid, but it is necessary to give a seemingly excessive opacity to compensate for the loss of fixing. Any "forcing" of development through under exposure is to be carefully avoided in lantern slide work. The development should bring out the detail steadily through the various graduations, until the extreme highlights appear, and these should remain perfectly clear while the slide is acquiring sufficient opacity.

When development is judged complete, the slide is quickly placed, without any washing, in an acid fixing bath. It is a mistake to submit lantern slides to a washing process between development and fixing, as during the process the slide acquires sufficient density to cover the highest lights that have been so zealously guarded. I am aware that many hands have been uplifted against the use of an acid fixing bath, and probably will be continued to be raised until the end of the tale. My own experience is absolutely in its favor, and I have constantly employed it in the form given below for the last fourteen or fifteen years. For lantern slide work I particularly recommend its employment. Fading, marks of any and every description, have at various times been attributed to its employment, but in my fifteen years experience I have never found either a negative or lantern slide fade, and I see no reason, if properly made, for an acid fixing bath to cause fading.