. The book of photography; practical, theoretical and applied. band J,which travels through a vessel of water Kand effectually removes any emulsion thatmay find its way on to the back of theplate. This band also touches the band F,for the same purpose. The bands f and Jare made of rubber, but the band L is madeof woven wire, in order that the platesmay be cooled at maximum speed. Thetunnel chamber :m is about 15 ft. long, sothat the setting or stiffening of the platemay be assured before it is removed fromthe endless band. This is the kind ofmachine in use in many large factories,and with it a
. The book of photography; practical, theoretical and applied. band J,which travels through a vessel of water Kand effectually removes any emulsion thatmay find its way on to the back of theplate. This band also touches the band F,for the same purpose. The bands f and Jare made of rubber, but the band L is madeof woven wire, in order that the platesmay be cooled at maximum speed. Thetunnel chamber :m is about 15 ft. long, sothat the setting or stiffening of the platemay be assured before it is removed fromthe endless band. This is the kind ofmachine in use in many large factories,and with it an enormous amount of coatingmay be done in a surprisingly short spaceof time, with absolute uniformity andpiecision. Melting Down Stock Emulsion. From the description given, it will beseen that the operation goes on almostautomatically, little or no attention beingnecessary beyond seeing that the emulsiontrough is kept filled from the reservoirabove, and that the plates are removedfor drying when they reach the end of theice-chamber. In working on so large a. Fig. 148—Emulsion scale, it is usual to make a stock emulsionand to melt it down as required. To facili-tate this, an emulsion press (Fig. 148) isused. The emulsion is placed in this, andis squeezed through holes in the bottomby means of the plunger. The body of thepress and the plunger are made of analuminium alloy, which does not affect theemulsion — an important considerationwhich ought not to be overlooked. THE BOOK OF PHOTOGRAPHY. Emulsions Ripened with Ammonia. Fairly rapid plates may be made withoutemploying the boiling process at all, bytreating them with ammonia. Such plates,although not extremely sensitive, are con-siderably quicker than collodion may be prepared by treatment at atemperature of about 100° F., or the emul-sification and subsequent treatment maytake place at ordinary temperature. Theformer does not appear to possess any ad-vantage over the usual method of boiling,but the la
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