. The half-tone process. A practical manual of photo-engraving in half-tone on zinc, copper, and brass. venby the manufacturers. The lamps are supplied inamber and ruby. For three-colour negative making, where it is veryimportant to be able to have the illumination of such acolour as the plates will be insensitive to, it is desirableto have a separate small lantern of the kind shown infig. 31, so that, if necessary, different screening glassescan be put in. Special frontscan be made up by coatingglass with coloured is called a safe lightfor three-colour work is madeup of two and
. The half-tone process. A practical manual of photo-engraving in half-tone on zinc, copper, and brass. venby the manufacturers. The lamps are supplied inamber and ruby. For three-colour negative making, where it is veryimportant to be able to have the illumination of such acolour as the plates will be insensitive to, it is desirableto have a separate small lantern of the kind shown infig. 31, so that, if necessary, different screening glassescan be put in. Special frontscan be made up by coatingglass with coloured is called a safe lightfor three-colour work is madeup of two and sometimes threeglasses or films, and formsa very dense ruby exact colours and finalcombinations have to be de-termined by spectroscopictests. A narrow bench down eachside of the room is necessary,one side being kept clear forfilling the dark slide, whichshould lean against the wallof the room when being filled. To avoid the dark slideslipping off the bench through being inclined at toogreat an angle, it is desirable to fasten a fillet of woodon the bench to stop the slide. A place should. 82 THE HALF-TONE PROCESS. be reserved, also alongside, for the lid of the slide,which, if put down on the floor underneath, is aptto get kicked, owing to the darkness, and therebysplit or broken. A drawer or two under the bench to contain dusters,polishing cloths and leathers, cotton wool, filter papers,and other things which should be kept dry and clean,is a convenience. The position of the bath when the wet plate pro-cess is used should be as near as possible to the darkslide, and as far as possible from the developing sink,so as to obviate splashes of developing or other solu-tions finding their way into it. The position should besuch, however, that a good light falls upon it, so thatone can easily see to put the plate in and take it a dipping bath is used, the mouth of it should belevel, or thereabouts, with the bench. Better still is the plan* of having a box for the bat
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