. Practical photography : being the science and art of photography, developed for amateurs and beginners . nd the water used for swabbing the floor should be clean, otherwiseit will leave behind it a crop of dust for the future. In fact, one eannotbe too careful. A blouse of unbleached holland is the best overall to wearin making plates, and not clothing of dyed material. There is no doubtthat what is termed unwashed or crude emulsion would be equallyliable to give spots of similar kind to the washed emulsion did not theaction of the washing water immediately set the film in hard pellicle, and
. Practical photography : being the science and art of photography, developed for amateurs and beginners . nd the water used for swabbing the floor should be clean, otherwiseit will leave behind it a crop of dust for the future. In fact, one eannotbe too careful. A blouse of unbleached holland is the best overall to wearin making plates, and not clothing of dyed material. There is no doubtthat what is termed unwashed or crude emulsion would be equallyliable to give spots of similar kind to the washed emulsion did not theaction of the washing water immediately set the film in hard pellicle, andthus envelope the bromide of silver in an impenetrable casing. This may, perhaps, account for the absence of spots in plates preparedwith a washed emulsion and a preservative. It must be borne in mind that until the ether and alcohol haveevaporated from a plate coated with a washed emulsion, the film is in asoft and permeable state, and the feeble affinity which binds the bromineto the silver is insufficient to prevent a partial reaction when in thatstate it comes in contract with a suitable CHAPTEE VIII. The Gelatino-Bromide Process—Introductory—NecessaryApparatus, &c. The essential difference between the gelatino-bromide process and thevarious collodio-bromide processes detailed in the preceding chapter,is, as has already been pointed out, that in the former a solution ofgelatine takes the place of collodion as a medium of suspension forthe sensitive salts. Upon this fact hinge several important drawback of collodion emulsion is that, owing to its peculiarstructure, the salts of silver can only with difficulty be introduced in asufficiently minute state of division for practical purposes. This is adifficulty which the beginner in emulsion work will probably take somelittle time to completely master. In gelatine emulsion, on the contrary,this drawback almost entirely disappears. The peculiar feature ofgelatine emulsion is that it holds the silver
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