Temperature of developer 4-8° C. 16-17° C. 26-28° C. Time of development 1 min. 3° W. 8° W. 13° W. " " 2 min. 9½° W. 10° W. 15° W.
Temperature of developer 1-2° C. 26-28° C. Time of development ¼ min. 6° W. 10° W. " " 3 min. 14° W. 15° W.
The collodion process is still preferred for reproducing black and white designs, drawings, engravings, etc., where very dense negatives are desirable. The fixed and washed plate is put in a bath of bromide of copper (ten per cent. solution); the film whitens immediately, and when the color is even all over, the plate is taken out and plunged into a bath of the ordinary ferrous oxalate developer. It takes a dark olive tint, which is very non-actinic, the shadows meanwhile remaining very clear.--_Photo. News._
GELATINO BROMIDE EMULSION WITH BROMIDE OF ZINC.
By this time of the year I have no doubt many, both amateur and professional photographers, are either contemplating or are actually at work making their stock of plates for the coming season, and it is to be hoped that we shall have more favorable weather than we had last year.
Some four or five years since I tried using bromide of zinc instead of the ordinary salts, namely, bromide of ammonium or potassium. I only made one batch of plates at the time, which possessed several important features I considered an advantage, and I think well worth while following out. I do not think it can be denied that ordinary gelatine plates, if exposed in a weak light, fall very short of the results obtained with wet collodion when compared side by side, gelatine being almost useless under these conditions, and there is a decided gain in the result in this respect if the emulsion be made with zinc bromide.
In using bromide of zinc there is a slight difficulty to overcome, but it _can_ be overcome, as I have succeeded in making a perfect emulsion. It will, I have no doubt, be remembered that Mr. L. Warnerke was the first to call attention to this salt in the days of collodion emulsion; and I think he claimed for an emulsion prepared with it that the image would stand more forcing without fogging to gain any amount of intensity. This was said of a collodion emulsion, and I also find that it is the same when used in a gelatine emulsion. I have heard a great many say, when speaking about the intensity of gelatine plates, that they can get any amount of intensity. I grant that in a studio where the operator has full command over the lighting of his subject by means of blinds, but it is not so in the field, especially when the light is dull. I have seen thousands of negatives, and as a rule I have found want of intensity has been the fault, and generally through the light. Now if we can find a remedy for this, it will be a step in advance.