PHOTOGRAPHIC CORRESPONDENCE.
Box Sawdust for Collodion.—The following will be of some use to your photographic readers:
I find that, by treating box sawdust with nitric and sulphuric acid (in the same manner as cotton), and then dissolving it in ether, it gives a far more sensitive collodion than either cotton or paper, and the pictures produced by it are of unequalled brilliancy.
Can you inform me whether portraits can be taken for sale, by the collodion process, without infringing upon the patents?
Chas. Whitworth.
Henrietta St., Birmingham.
Proportions of Chlorides and Silver.—I trust you will allow me space in your valuable work for some remarks in reference to an important photographic query, viz. What are the proportions of chlorides and silver uniformly suited to give the best positive pictures?
I am led to propose this subject for the consideration of practical photographists, and, if possible, that amateurs may arrive at something like a rule to guide them in printing positives that will please.
The necessity of these remarks, to me at least, appear very evident from the wide space which stands between the proportions proposed by various operators. Mr. Lyte, "N. & Q.," Vol. ix., p. 158., says 42 grains of chloride and 100 grains of silver to 1 oz. of water. Mr. Pollock, "N. &Q.," Vol. vii., p. 588., says 20 grains chloride, and 90 grains of silver to the ounce. Mr. Hockin has 10 grains chloride, silver 60. Mr. Delamotte, for albumenized paper, chloride 60 grains, silver 120. Mr. Thornthwaite begins as low as chloride ½ grain, and silver 30 grains; and lastly, amidst a long range of proportions, from 1 grain of chloride to the ounce, and silver 20 grains to the ounce, Dr. Diamond, a great authority in photography, assures all that the best results can be obtained by using of chloride 5 grains to the ounce, and of silver 40 grains to the ounce. If so, let the photographic world know that the latter proportions are sufficient, and the others needless, wasteful, and expensive without cause. I trust you agree with me in thinking that it would be of use to a large number of beginners to have the proportions best suited for printing positives defined as near as possible, and not be left to guess at proportions varying from ½ grain to 60 grains, and from 20 to 120. I have written hurriedly, and hope you will see the object I aim at.
Amateur.
Photographic Copies of Rembrandt.—The extreme rarity and great pecuniary value of many of Rembrandt's finest etchings are doubtless well known to many of our readers, as being such as to put these master-pieces of art beyond the reach of ordinary purchasers. This series of works, calculated beyond all others of their kind to delight the possessor, will however, thanks to photography, soon be obtainable by all admirers of the great master. Two distinguished French photographers, the brothers MM. Bisson, have succeeded in obtaining, by means of this wonderful art, copies of a fidelity attainable by no other process: so that the wondrous lights, shades, half-tones, and chiaro-obscuro, for which Rembrandt is so remarkable, are preserved in all their original beauty. The plates will be accompanied by descriptive letter-press, and by a Biography of Rembrandt from the pen of M. Charles Blanc. As the works are so numerous, the first series will consist of forty plates, to be issued in ten livraisons, each containing four plates, price twenty francs; a very moderate sum, if we remember that among the works thus to be issued, at a cost of five francs each, will be found copies of such gems as the Avocat Tolling and the Pièce de Cent Florins.
Coloured Photographs.—I have lately seen, and very much admired, some specimens of photographic coloured portraits. They have all the broad effect of the great masters perfectly in detail, and none of the niggling effect of many coloured photographs, which are in fact specimens of miniature painting rather than photography—the outline alone being given by the photographic art. The specimens I refer to appear to have been soaked in oil, or some transparent varnish, and then coloured in separate tints, probably from the back; the shadows being entirely photographic. It is evident they are quickly and easily executed; but I am desirous of knowing the exact process, and shall be much obliged for information on the subject.
An Amateur.