A manual of photographic chemistry, theoretical and practical . e plate is now placed on the silverwires of the frame, taking care that the draining ends be towardsthe bottom. In carrying the dark frame to and from the cam-era, and at all times when the plate is inside, make sure thatthe slide is kept in such a position that no liquid can run backover the film. If this precaution be not attended to manysorts of defects will be visible in the picture. The frame tooshould be carried very gently, else particles of dust and abradedwood might be set loose and settle on the surface of the
A manual of photographic chemistry, theoretical and practical . e plate is now placed on the silverwires of the frame, taking care that the draining ends be towardsthe bottom. In carrying the dark frame to and from the cam-era, and at all times when the plate is inside, make sure thatthe slide is kept in such a position that no liquid can run backover the film. If this precaution be not attended to manysorts of defects will be visible in the picture. The frame tooshould be carried very gently, else particles of dust and abradedwood might be set loose and settle on the surface of the would give rise to spots in the picture either of a trans-parent or opaque character, according to the nature of the im-purity which causes them. All the observations contained in this chapter apply both tocollodion negatives and positives taken in the camera. In thenext two chapters we must make a distinction between thetwo processes and describe them separately, because in somerespects the treatment which is best adapted for the one willnot suit the CHAPTEE XIII. THE POSITIVE COLLODION PROCESS ON GLASS OR METALLICPLATES (ferrotypes). We have previously detailed the various operations andchemicals necessary before obtaining a positive picture by de-velopment, viz., cleaning the glass, the collodion, the sensitiz-ing bath, the developers, the fixing agent, and the general ob-servations contained in last chapter. It now remains for us todescribe those manipulations wherein the positive process dif-fers from the negative. These consist mainly in the develop-ment. In developing; a glass positive the solution of sulphate ofiron should be flowed evenly over the film, and in some quan-tity, so as to wash off a portion of nitrate of silver into the the case of negatives it is an object to save every trace ofnitrate, and precipitate it upon the image, in order to increasethe density; but with positives there is a fear of getting anexcess of intensity, and if the collod
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Keywords: ., bookcentury1800, bookdecade1880, bookidma, booksubjectphotography
