=Hard Gelatine.=—Plates prepared with this, show after drying, a shiny, transparent film, more or less according to the quality. Such plates give hard prints, and are soon used up in printing, the finest and even the middle tints becoming weaker, and the shadows gradually coalescing, specially in the case of short exposure and very dense negatives, and they are generally useless after a few impressions have been taken. If ammonium bichromate is used, together with hard gelatine, then, as a general rule, it is impossible to obtain more than one or two prints from each plate. By washing the gelatine, these inconveniences are not at all removed, no matter which of the two salts has been used. =Soft Gelatine.=—If this is prepared with potassium bichromate, then the plates will have a dull but rough and untransparent film, which will be found very unserviceable for printing, as the prints will lack vigour; the high lights will tone, and the whole picture appear blurred. If, however, ammonium bichromate is used in conjunction with soft gelatine, the plates will also have a dull appearance, but though they work somewhat better than those prepared with potassium bichromate, they will not be of sufficient durability, the finer tones soon disappearing during printing. Therefore, neither hard nor soft gelatine are suitable for Collotype work, as the printing operations are rendered more difficult. If both sorts are mixed, the results will be somewhat better, but not like those obtainable with middle hard gelatine, which must be accepted as the most suitable kind for Collotype work.