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 this, they are placed one by one in water of from 80 to 100 degrees Fahrenheit. This immediately loosens the backing paper upon which the tissue-compound was originally coated, and which, having now completed its office of supporting the tissue until it is no longer needed, is stripped off. It is separated from the tissue at one edge, and lifted gently away. If it still adhere tenaciously, a little longer soaking in the warm water will be necessary to effect the removal of the paper; but this is always a bad sign. The back surface of the tissue, opposite to that which was exposed, is now uncovered; and the next operation is to remove all gelatine, pigment, and chromic salt which have not been rendered insoluble.

The operation of developing, up to this period, has been conducted in a subdued or yellow light. As the sensitive surface is now exposed, it is obvious that strong white light should be avoided until the bichromate has been washed out of the film. This is rapidly done. A large portion has been removed whilst the print was soaking; and now that the gelatinous compound is exposed to the warm water, the salt is rapidly diffused in the water. The process of clearing may be accelerated by allowing a gentle stream of the warm water to fall on the surface of the print, or by laving the water on to it with the hands, so as to produce slight attrition between the surface and the water. This, however, is not necessary, as, if the print be left face down in the warm water, it will be found, in the course of from five minutes to a quarter of an hour, to have parted with nearly all the superfluous gelatine and color, presenting the image in all its proper gradations, and only requiring a little further washing to complete the operation.

The usual temperature for development is from 80 to 100 degrees, Fahrenheit; but there are circumstances