PHOTOGRAPHIC CORRESPONDENCE.

Three New Processes by Mr. Lyte.—Will you kindly allow me room in your pages for the insertion of the following three processes, which may not, perhaps, be uninteresting to some of your readers? The first is respecting a very excellent combination with which to excite collodion. The second is on the subject of a capital developing agent, and, I believe, a partially new one. The third, a certain improvement in the production of positives on albumen paper.

To make my collodion, I use the Swedish filtering paper, as recommended by the Count de Montizon, Mr. Crookes, &c., not so much on account of its superior properties, as the easier manipulation, and the greater certainty of obtaining a completely soluble substance. Having obtained a clear and tolerably thick collodion, take

Rectified spirits of wine1oz.
Iodide of ammonium45grs.
Bromide of ammonium12grs.
Chloride of ammonium1gr.

Iodide of silver, freshly precipitated from the ammoniated nitrate, as much as the solution thus produced will take up—a small excess, which will settle at the bottom, will not signify. Nearly the same compound, one which is equally good, is produced as follows. Take

Rectified spirits of wine1oz.
Iodide of ammonium50grs.
Bromide of ammonium12grs.
Chloride of silver5grs.

Whichever of these two sensitizers is used, take 1½ drachms, and add to every ounce of the collodion.

Collodion thus prepared is most rapid in its action, giving a deep negative (with Ross's sixteen guinea lens, and the developing agent I shall hereafter describe) in ten seconds in clear weather, and instantaneous positive pictures, which may be afterwards darkened with the solution of terchloride of gold, in chloride of ammonium. It does not easily solarize, and, what is best of all, gives the most pleasing half-tones.

I find it preferable, in taking landscapes, to rather increase the quantity of the iodide of ammonium, in order to give complete opacity to the sky; but if the operator pleases, he may produce the most admirable effect with the above-named proportions, by painting in clouds at the back of the plate with Indian ink: and this latter plan is preferable, as the addition of more of the iodide lowers the half-tones.

If more of the chloride than above specified be added, it will cause the plate to blacken all over during development, before the extreme lights are fully brought up.

My developing agent is made as follows. Take

Distilled water10oz.
Pyrogallic acid6grs.
Formic acid1oz.

The latter is not to be the concentrated acid, but merely the commercial strength. These, when mixed, form so powerful a developing agent, that the picture is brought out in its full intensity, almost instantly, while at the same time all the deep shades are quite unaffected, and the half-tones come out with a brilliancy I have never seen before.

Another excellent developing agent is composed as follows. Take

Distilled water10oz.
Sulphuric acid3drops.
Protosulphate of iron½oz.
Formic acid1oz.

The formic acid is also a most capital addition to the protonitrate of iron, and either this or the former liquid produce most brilliant positives leaving a fine coating of white dead silver. I may also make mention of the improvement I have made in the albumen paper, which consists in the introduction of the chloride of barium into the albumen, in place of chloride of ammonium or chloride of sodium. Take

Water6oz.
Albumen6oz.
Chloride of barium7¼dr.

Whip these up, till they are converted entirely into a white froth; when this has settled into liquid, pour it into a tall jar, and allow the precipitate, which will then separate, to settle completely, and strain the supernatant liquid through fine muslin. The paper, being laid on the surface of this fluid for a space of from five to ten minutes, may be taken off and hung up by a crooked pin to dry, and then ironed. It is to be sensitized with nitrate of silver, 120 grains to the ounce of water. The setting liquid I use is prepared according to the formula given by me in Vol. vii., p. 534. of your journal, except that I prefer to use half to one grain of pyrogallic acid, and 120 grains of chloride of silver. This paper must be soaked for a few minutes or so in rain water, after being printed, before being placed in the hypo.; the presence in the water of any salt seems to destroy the tone of this paper.

Florian, Torquay.

Muller's Processes—Sisson's Developing Solution.—I am glad to find that I have called the attention of your photographic correspondents to Mr. Muller's process, as detailed in The Athenæum of Nov. 22, 1851, which seems to have been strangely overlooked and neglected. As your correspondents have induced you to reprint the article, perhaps you will also yield to my request, and reprint an article from the same journal of later date (Jan. 10, 1852) containing another process, more economical and more sensitive than the other, invented also by Mr. Muller, and the value of which I have proved. In that, as in the other, there is no developing agent required. To save time I have copied from my note-book the article itself, and append it to this communication.

A photographer of several years' standing informs me that my developing solution produces excellent negatives upon glass, and that he has been trying it as a bath with success. He writes me:—"I use your developing solution for negatives only; and by using a very small opening, say about 3/10ths of an inch diameter, single achromatic lens, I have produced negatives in one minute, which print most beautiful bright positives. The views I have taken and developed with your solution were without sunshine, the sky very cloudy, three o'clock p.m. The collodion was prepared by Messrs. Knight & Son."

Since I received his letter I have tried a negative so developed, with the best success; and I attribute the success to the fact that you may go on developing with that solution any length of time almost, without any fear of spoiling the negative, thus getting thickness of deposit; and that the deposit on pictures taking so long a time to develop has a very perceptible yellow tinge, which, like the gold in Professor Maconochie's method (detailed in Photographic Journal for this month), stops the chemical rays.

J. Lawson Sisson.

Edingthorpe Rectory.

"Patna, India, Nov. 9, 1851.

"Plain paper is floated on a bath of acetonitrate of silver, prepared of 25 grs. of nitrate of silver, 1 fluid oz. of water, 60 minims of strong acetic acid. When well moistened on one side, the paper is removed, and lightly dried with blotting-paper; it is then placed with the prepared side downwards on the surface of a bath of hydriodate of iron (8 grs. of the iodide in 1 oz. of silver). It is not allowed to remain on this solution, for if this were the case it would become almost insensitive. The silvered surface must be simply moistened with the hydriodate—the object being to get a minimum quantity of it diffused equally over the silvered surface. The photographer accustomed to delicacy of manipulation will find no difficulty in this. While still wet the paper is placed upon a glass (face downwards), and exposed in the camera for periods varying from 10 to 60 seconds, according to circumstances. In sunshine, and when the object to be copied is bright, 5 seconds in this climate (India) is sufficient. Excellent portraits are obtained in shade in 30 seconds; 60 seconds is the maximum of exposure. The picture is removed from the camera and allowed to develop itself spontaneously in the dark, then soaked in water, and fixed in the usual manner with the hyposulphite of soda."—Athenæum, Jan. 10, 1852.