The Art and Practice of Silver Printing by Henry Peach Robinson William de Wiveleslie Abney

Author:Henry Peach Robinson , William de Wiveleslie Abney
Language: eng
Format: epub
Publisher: E. & H. T. Anthony
Published: 1881-03-25T05:00:00+00:00

common salt. The salt forms chloride of silver, which gradually precipitates, and the clear water is then drawn off on the next day, and the sediment is left undisturbed.

It now remains to see which toning bath is to be used. If No. 1 or 3, the whole of the free silver should as far as possible be washed away, which may entail three or four changes of water; the last two washings it will hardly repay to place in the tub; the second washing should certainly be added to it. If No. 2 toning bath*be used, a little free silver should remain in the print; in fact, the washing should be confined to two changes of water.

When toning operations are commenced, the toning solution is poured off from any sediment that may be in the bottle containing it into a dish a couple of inches wider each way than the

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largest print wMch has to be toned. If big prints have to he ' toned, it is inadvisable to place more than a couple in the dish at the same time, since there is a certain awkwardness in judging of the amount of tone given to a print which is (say) between two or three. The prints should be placed face up in the solution, and great care should bo taken that liquid separates each print from thp next one to it, otherwise there will be patches of unequal toning. The dish containing the prints in the solution should be gently rocked to secure a proper mixture of the solution which may have been robbed of its gold in those strata next surface of the prints. The rocking is also advisable to cause any adhesion between two deep-toning prints impossible. If the prints be of small size, a dozen or more may be toned at one operation. Each print should be frequently brought to the surface of the liquid, and examined in order to see how the toning action is progressing. When one print is judged sufficiently toned, it is removed to a dish containing pure water, and another untoned print placed in the dish in its stead. This operation is continued till all the prints are toned. We have heard that it has been suggested to place the prints" in water containing a littler acetic d^id or -common salt, in order to stop the toning action continuing from the solution which may be held in the paper. The former is most undesirable, acetic acid, as we shall jsee presently, decomposing the fixing bath.

As to the addition of common salt, we can scarcely give a favourable opinion regarding it. The addition of a chloride docs, in truth, slier the colour of the deposited gold (see anU)y and it may be this that gives rise ta the opinion that it corrects toning aotion. Of one thing we have little doubt, howevef, and that is, that the addition of any Large amount of common salt will tend to turn the albumenate of silver into chloride, which in fixing will materially weaken the print.

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