A Manual of the Collodion Photographic Process - The Whitening Process

Contents

Part 1

Part 2

PART III

The Whitening Process

The picture being thoroughly washed in plenty of water, after fixing with hypo-sulphite of soda, is treated in the following manner.


Prepare a saturated solution of bi-chloride of mercury in muriatic acid. Add one part of this solution to six of water. Pour a small quantity of it over the picture at one corner, and allow it to run evenly over the glass. It will be found immediately to deepen the tones of the picture considerably, and the positive image will almost disappear; presently, a peculiar whitening will come over it, and in a short time a beautifully delicate white picture will be brought out.


The negative character of the drawing will be entirely destroyed, the white positive alone remaining. This picture after being well washed and dried, can be varnished and preserved as a positive; but nevertheless, even after this bleaching, it can be
changed into a deep-toned negative, many shades darker than it was originally, by immersing it, after a thorough washing, into a weak solution of hypo-sulphite of soda, or a weak solution of ammonia. The white picture will
vanish, and a black negative will be the result.


It is very singular that the picture can be alternately changed from a white positive to a black negative, many times in succession, and very often with improvement.
Thus, by the above process, a most perfect white positive or a deep black negative is produced, quite distinct from each other.


In the first part of this after-process it will be observed, that the effect of this bi-chloride of mercury solution is to deepen the shades of the picture, and this peculiarity can be made available to strengthen a faint image, by taking the precaution of using the solution weaker, in order that the first change may be completed before the whitening effect comes on.


The progress of the change can be stopped at this point, by the simple application of water.