The Optical Magic Lantern Journal (June 1890)

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The Optical Magio Lantern Journal and Photographic Enlarger. 5 adhere to one stundurd strength of developer ; and for “contact” printing one fixed distance from the light for exposure, and produce the tone desired solely by the time of exposure. If this plan is adopted I am sure much more satisfactory results will be obtained than by continually altering the strength of the developer, ris varying the distance the plate is held from the ight. Most of the slides prepared by professionals are made by the collodion or wet-plate process ; very fine slides are also made by collodion-albumen. It is generally considered that there are no lantern slides at all equal to those made by one or other of | the collodion processes. No doubt for brightness and “‘sparkle ” collodion slides are difficult to surpass ; but there is often a want of half-tone about them, consequently little gradation between the high lights and shadows. process a very hard race; and I venture to think (though it may be considered somewhat heterodox to even throw out the mere suggestion) that for softness ; and half-tone the gelatine plate holds the field. There j are many good inakes ot plates on the market, and for | those who do not care to make their own, I would say, | Try several makes, and then stick to those you find : give you the best results. I may say in passing that gelatino-chloride plates are of no use for reducing, as they are far too slow. Lantern plates are usually developed by ferrous| ‘oxalate, pyro and ammonia, pyro and washing soda, | or hydroquinone. Formerly ferrous-oxalate was the favourite developer for lantern plate work, but it is not | so much used now; the tones produced by it are always of a cold grey, and considerable care is required when working with it, for the slightest contact of hypo will ‘cause a fog to spread over the plate. Pyro and ammonia isa favourite developer with many workers ; ‘some add a little carbonate of ammonia to obtain red tones. A very good developer, and one easy to work with, is washing soda and pyro. It gives pleasing ‘tones, but it has, however, the disadvantage of often leaving a yellow fog on the plate, which must be re‘moved by a clearing solution, and unless considerable care is used in clearing, many of the finer details may be entirely removed, and if allowed to remain in the solution too long the plate loses its sharpness, and looks very flat when shown on the screen. Hydroquinone has now come into great favour as a developer for lantern plate work, and is the one I prefer to all others. and the slides require no clearing after development, unless they have been taken from thin or faulty nega: tives, when a little local clearing by means of a camel’s ; hair brush may be required. : The formula that I like the best is one given by Thomas and Co., with their plates, viz. :— No. 1.—Hydroquinone, 16ogrs. ; sulphite soda, 20z.; ‘brom.amm., 2ogrs. ; citric acid, Gogrs.; water to 2002. _ No. 2.—Carbo. potash, 20z.; carbo soda (crystal‘ised), 202. ; water to 200z. Use equal quantity of each. I generatly develop four plates with 2}0z. of solution. I have developed as many as 10; but four are quite sufficient, for after that number the developer becomes very slow, and has a tendencyto “block” the Shadows. Eikonogen is said to produce verv similar results to shydroquinone. The gelatine plate is running the collodion | ‘there for a few minutes after all whiteness has dis| appeared, so as to ensure thorough fixation. It gives absolutely clear glass, | It is better to develop slides by artificial light rather than by daylight passing through some non.-actinic medium ; for daylight is so variable in its intensity that it renders it very difficult to judge the proper density of the slide in consequence, whereas by artificial light you can have one fixed standard, and develop the slides to pretty nearly an equal density. It is desirable to develop a little denser than required, as the slide loses a little of its density in the fixing bath. Immediately after placing the plate in the developing solution, pass a camel’s hair brush (kept in a cup of water near the developing dish) rapidly over the plate, to remove any small air-bubbles which may be on the surface of the film. After development the plate requires a good wash under the tap, and should then be placed in the fixing bath ‘hypo, 402. ; water, 2007.) and allowed to remain Wash again after removal from the fixing solution, and place it for a short time in a saturated solution of alum to harden the film. If working with hydroquinone, on no account place the plate in the alum solution before fixing, or you may obtain a result not to be desired. If from any error in exposure, or the slide is taken from a thin negative, causing it to be opaque, when there ought to be clear glass, this opacity may be removed with a little care and patience by the aid of the following clearing solution : Sulphate iron, 30z. ; alum, roz. ; sulphuric acid, 10z.; water, 200z. Pour a little of this solution into a small dish, and place a basin containing clean water near, then holding the plate in the left hand with the sky or fogged part slanting downwards, so as to prevent the clearing solution running into the details of the picture. Paint with a small brush the clearing solution over the fogged part of the plate until it becomes quite clear, frequently dipping the plate into the water during the process, to prevent the clearing solution spreading over the plate. Any over dense shadow may also be reduced in this way. Before doing this, take care the slide has been in the alum bath. Lantern slides must be quite free from fog or veil, and the above method will quite remove this defect, and if care is used the details of the picture will not be injured. GODFREY BINGLEY. (To be continued.) 10: A Rival to the Electric Light. Ir the invention of Mr. W. J. Norton, of Pittsburgh, fulfils its promise, there is a dangerous rival of the electric light in the field, if not to petroleum. He has invented what is alleged to be the cheapest light ever known, and yet “a light as intense and as accurate in its illumination of colours as the sun at noonday.” It is claimed that 5o00-candle power light of the kind in question can be run at the nominal cost of one cent an hour. Mr. Norton has for years been engaged in developing this light. The undertaking has been very quietly conducted. Recently he permitted a few capitalists to witness experiments with his device. These tests proved so successful that a temporary and