Mr. Archer's Services to Photography.—In Vol. vii., p. 163., Mr. Horne seems very indignant at the idea that Mr. Archer taught him to take pictures, and says Mr. Archer's published account will not succeed. Now I know that Mr. Archer and myself did take pictures by his process as published. I also assert that neither Mr. Horne nor Mr. Fry made any collodion pictures before Mr. Archer published his account in The Chemist, and, with the ordinary camera, that process must be the one now to give any chance of success, for without washing the plate the collodion will not keep five or six hours without staining. But as that process was not sufficiently quick, Mr. Archer proposed to take the pictures in the bath itself; and I have one which I took in that way on the 16th of May, 1851.
Mr. Horne, I think ungenerously, wishes to detract from Mr. Archer's merit, and to exalt himself and Mr. Fry at Mr. Archer's expense. I have a letter of Mr. Fry's, dated March 23, 1852, in which he says, "I with much pleasure accord to Mr. Archer the credit he is fairly entitled to, of being the sole inventor of the collodion process." And another letter, wherein he says he "never sanctioned the insertion in any work of any article connected with the collodion process." I also know that Mr. Archer prepared collodion for Messrs. Horne; that Messrs. Horne advertised it as prepared by Mr. Archer; and that they were glad, when the thing was new, to avail themselves of Mr. Archer's assistance.
W. Brown.
Ewell.
Mr. Weld Taylor's Iodizing Process.—The process I generally adopt in iodizing paper by the
ammonio-nitrate of silver, I have found to be the most certain of all, and I here give a formula for the benefit of your readers. They will find it admirably adapted for any objects in the shade, or any not lit by the sun's rays; it also has an excellent quality, of not darkening by exposure in the camera, as most other papers do. I have taken negatives with it all the winter, even at Christmas. It is rather slow, but certain; and as your readers try it and improve it, I hope they will communicate the results.
It rests alone on the superior sensitive property the nitrate of silver possesses after being redissolved in ammonia, which every photographer must have experienced. And it has, I believe, in prospect, the dispensing with the crystals of nitrate of silver, and simply at last employing silver leaves, which will save a great expense to the operator. The first solution is, to the proportion of a wine-bottleful of water add three grains of pure tannin, well dissolved in filtered water. Upon this float every sheet of paper, taking care of bubbles when they are to be hung up to dry. Do a great number; they will be ready for the ultimate process. Make now a solution of nitrate of silver, twenty-six grains to the ounce: if three ounces are to be made, dissolve the nitrate in half an ounce of distilled water, and add liq. ammo. fortissimus till the precipitate is redissolved. Then fill up with two and a half ounces of distilled water. This is the formula of Mr. Alfred Taylor. With this solution pass over every sheet with a brush: it cannot be floated, as exposure to the air precipitates the silver. The iodizing solution is,—
| Iodide of potassium | 250 grs. |
| Fluoride of potassium | 20 grs. |
| Cyanide of potassium | 15 grs. |
| Muriate of soda | 30 grs. |
to a full half-pint of distilled water.
The success of the operation depends upon this point, that the latter solution must be laid over the first, before the first has entirely dried, or at that point when all appearance of wet is absorbed. Three sheets of paper may be washed over at a time; and as the corner where the solution runs to is apt to remain wet longer than the rest of the paper, the drip may be assisted off with a bit of blotting-paper. Also, before the second solution is dry, it is to be floated on water; but the same conditions must be strictly observed. When it has floated a short time, "it does not require so long a time as the acid process." It is, while wet, floated again upon a weak solution of free iodine for about half a minute; it may then be dried, and is ready for the sensitive solution. This last must be acid, and any of the approved formulæ will suit it; but the solution, whatever it is, must be allowed to dry before placing between the white glasses, nor on any account ought it to be touched with blotting-paper. The image is to be brought out with gallic acid and acetic acid, laid over with a brush, and requires no heat. It is of a very red colour generally, but that does not impair its effectiveness in taking the positive impression.