No. 1.

Mercuric chloride.......

100 grains.

Potassium bromide........

100

Water (distilled) ........

10

In this the negative is bleached and is then thoroughly washed as in previously described methods. It is then blackened in a solution made by combining the two following :No. 2.

Silver nitrate ..........

100 grains.

Water (distilled) ........

10 ounces.

No. 3.

Potassium cyanide........

100 grains.

Water (distilled) ........

1 ounce.

No. 3 is added gradually and with constant stirring to No. 2. At first a heavy white precipitate is formed, which is dissolved on the addition of the cyanide solution. Care should be taken not to add more than is sufficient to dissolve the precipitate, otherwise the blackening of the image will not take place satisfactorily. The solution should be poured into a dish and if running water is not at hand a large bowl or pail of water should be near by. The negative is immersed in the silver cyanide solution and at once the surface of the negative will blacken. After one or two seconds the plate should be lifted out and the back of it examined. In all probability the shadows only will be blackened, the lights and lighter half-tones remaining white. It is to be returned to the bath and again examined. Presently the half-tones will blacken and then the high-lights. Immediately the last trace of white has disappeared from the back of the negative the plate must be held under running water or plunged into the pail of water to check the action of the silver cyanide solution. Thorough washing should follow, and it will be found that the contrast in the negative has been greatly increased.

We now come to the case of under-exposed negatives, and it must be understood that comparatively little can be done in -such cases and only if the error in exposure has been slight. Nothing but the pencil can supply missing shadow detail. An under-exposed plate will develop slowly, the half-tone and shadow detail lagging long after the appearance of the lights. Many workers in such a case push development to the farthest in the hope of getting printing density. It is, however, a bad practice. If the subject is one with much contrast, the high-lights will be extremely dense, whilst the shadows will still be very thin and fog is almost certain to still further disfigure the negative. The print will show violent contrasts, the shadows being masses of solid black and the high-lights being simply spots of white paper. Negatives of this description may be improved (if not too bad) by the following method, but it is one that requires considerable judgment in applying it.

The following solution is made-

Chromic acid.........

30 grains.

Potassium bromide........

60 "

Water............

10 ounces.

In this the negative is thoroughly bleached and is washed in water till the deep yellow colour which it takes is discharged. One or two baths of a five per cent. solution of potassium metabisulphite will assist in getting rid of the colour. During these operations the negative should be well exposed to white light. The negative has then to be redeveloped, and a clean working developer should be selected. Metol, metol-quinone, ortol and glycin are all suitable. The object is to get rid of a portion of the density in the high-lights, which can be done in the following manner. When the developer is poured upon the plate the whole of the surface is converted once again to black metallic silver ; the action, however, proceeds slowly and may be examined from the back of the plate in the same way as in Monckhoven's intensification process. The shadows and the upper surface of the half-tones and high-lights are first converted to black metallic silver, whilst the lower portions of these two latter, being more deeply imbedded in the gelatine, take longer to develop. When from examination at the back of the plate it is seen that all but the highest points of light are redeveloped, the plate, without intermediate washing, is plunged into a freshly-made fixing bath, which removes the silver bromide left in the film and the lights are reduced in density.

If the action of the developer is carried too far, the contrasts will be just as violent as in the beginning ; if on the other hand it is checked too soon, the negative will be flat and thin. It is better to err on the latter side than on the former, as the error may be remedied by intensification, as in the case of an under-exposed,lightly-developed negative, to be considered next, while, although the operations just described may be repeated, irregularities of action are almost certain to ensue. Grease on the surface of the negative will also cause much trouble.