A Manual Of Photography

230 PRACTICE OF PHOTOGRAPHY. draw over it a piece of white paper to remove any dust or pelli- cle formed. When your operations are finished, you may pour hack the aceto-nitrate of silver into a hottie, and reserve it for another time. The necessity of employing M. Gray’s papers in a wet state is their most objectionable quality, hut certainly the results ob- tained by strict attention to his directions are often exceedingly beautiful. For developing the image the following is recom- mended, which does not, however, differ essentially from the developing processes already described. Make about a pint bettle of saturated solution of gallic acid, having acid in excess, and using distilled water ; decant a por- tion into a smaller bettle for general use, and fill up the other bottle ; you will thus always have a clear saturated solution. Four upon a slab of glass, kept horizontal, a little of this liquid, spreading it equally with a slip of paper, then apply the paper which has been exposed in the same manner as described for the negative paper, being careful to keep the back dry. Watch its development, winch is easily observed through the hack of the paper ; you may leave it thus as long as the hack of the image does not begin to spot.. When it is rendered very vigorous, remove it quickly to another clean slab, and well wash it in several waters, occa- sionally turning it, and gently passing the finger over the back; by this means you remove any crystals of gallic acid which might spot the picture. The appearance of the image at the end of this process will en- able you to judge if it was exposed in the camera the proper time. If it becomes a blueish grey all over, the paper has been ex- posed too long ; if the strongest lights in the object, which should he very black in the negative, are not deeper than the half tints, it has still been too long exposed ; if, on the contrary, it has been exposed too short a time, the lights are hut slightly marked in black. If the time has been just right, you will obtain a proof which will exhibit well-defined contrasts of black and white, and the light parts very transparent. The operation is sometimes accelerated by heating the gallic acid, and by this process the dark parts of the picture are rendered very black. To fix these negative proofs, a very strong solution of hypo- sulphite of soda, about 1 ounce of the hyposulphite of soda to 8 fluid ounces of water, is employed, and the picture is allowed to remain in it until every trace of yellowness is removed from tire paper.