PHOTOGRAPHIC CORRESPONDENCE.
Queries on Dr. Diamond's Calotype Process.—Would you kindly ask Dr. Diamond, to whom I should imagine all of us are more or less indebted, the following questions respecting the very valuable paper on the calotype in the last Photographic Journal?
1. As to the white spots which make their appearance in developing, on Turner's paper especially, and which he says are owing to minute pieces of metal in the paper, what is the best way of hiding them in the negative, so that they may as little as possible injure the positive? I have suffered sadly from this cause; and have tried to stop them with ammonio-nitrate, which turns after a time to red, and stops the light effectually; but I should prefer some black colouring the strength of which one could measure by seeing its immediate effect.
2. And again, when one has black spots, what is the best means of lessening their intensity, if not of wholly removing them?
Φωτογραφος.
[Where light spots occur in a negative, Dr. Diamond recommends, as the most effectual mode of stopping them, a little gamboge neatly applied with a camel-hair pencil. Where a great intensity is desired, Indian ink may be applied in the same manner, taking care in both cases to smooth off the edges with a dry brush. The cyanide of potassium applied in the same way, but with very great care, will remove the black spots. Before it appears to have quite accomplished its object, a negative should be immersed in water, as its action is so energetic.]
Albumenized Paper.—I have followed Dr. Diamond's directions for albumenizing paper (thin Canson negative) as accurately as I can, but I cannot prevent the albumen in drying, when pinned up, from forming into waves or streaks. This will be best understood from a specimen of a sheet which I inclose, and I shall be much obliged if you can tell me how this can be avoided. Some albumenized paper which I have purchased is quite free from this defect, but being at a distance from London, it is both convenient and economical to prepare my own paper.
C. E. F.
[We would recommend our correspondent to remove his paper from the albumen still more slowly; and to take care not to draw it along, but so to lift it that the last corner is not moved until it is raised from the albumen. In pinning up be careful that the paper takes the inward curl, otherwise the appearances exhibited will be almost sure to take place. As the albumenizing liquid is of very trifling cost, we recommend the use of two dishes, as by that means a great economy of time is obtained.]