PHOTOGRAPHIC NOTES AND QUERIES.
Le Grey and the Collodion Process.—As the claim to the invention of the collodion process is disputed, I think, in justice to Mr. Le Grey, whom all will acknowledge as a talented man, and who has done much for photography, that the claims he puts forth, and which I give, should be known to your readers who have not got his work, as they are in direct contradiction to Mr. Archer's letter in your 165th No. In his last published work, page 89., he states:
"I was the first to apply collodion to photography. My first experiments were made in 1849. I used that substance then principally to give more equality and fineness to the paper. I employed for that purpose a solution of iodide of potassium in alcohol of forty degrees saturated with collodion.
"In continuing these studies I was induced to apply this body upon glass, to obtain more fineness, and I was soon in possession of an extremely rapid proceeding, which I at last consigned to the pamphlet that I published in 1850, and which was translated into English at the same time.
"I had already at that time indicated the protosulphate of iron for developing the image, the ammonia and the fluorides as accelerating agents; and I was the first to announce having obtained by these means portraits in five seconds in the shade.
"The pyro-gallic acid is generally used now in place of the sulphate of iron that I had indicated; but this is wrong, that last salt forming the image much more rapidly and better, it having to be left less time in the camera.
"I believe, then, I have a right to claim for my country and myself the invention of this would-be English process, and of having been the first to indicate the collodion, and of giving the best method that has been discovered up to the present time.
"From the publication of my process, till my return from the voyage that I had made for the minister, I was little occupied in practising it, my labours on the dry paper having taken all my time. This has been used as a weapon against me, to make out that the first trials before setting out had been quite fruitless, as they had heard nothing more about it.
"Nevertheless, I have made my discovery completely public; and if I had practised it but little, leaving it to others to further develope, it has only been to occupy myself upon other works of which the public has still profited. It is then much more ungenerous to wish to take from me the merit of its invention."
G. C.
Ready Mode of iodizing Paper.—The readiest way I have found of iodizing the beautiful paper of Canson Frères, is the cyano-iodide of silver, made as follows: Twenty grains of nitrate of silver may be placed in half an ounce of distilled water, and half an ounce of solution of iodide of potassa, fifty grains to the ounce, added to the silver solution. Cyanide of potassa may then be added, drop by drop, till the precipitate is dissolved, and the whole filled up with four ounces of water. This solution requires but a very few minutes' floating upon water containing a small quantity of sulphuric acid; and it is then ready, after a bath of nitrate of silver, for the camera, and will not present any of the disagreeable spots so noticed by most photographers. This paper is probably the best for negative pictures we have at present; although, if very transparent paper is required, oiled paper may be used for negative pictures very successfully; or paper varnished is equally good. The oiled paper may be prepared as follows: Take the best walnut oil, that oil having less tendency to darken paper of any other kind, and oil it thoroughly. It must then be hung up in the light for a few days, the longer the better, till quite dry. It may then be iodized with the ammonio-nitrate, the ammoniated solution passing more readily over greased surfaces. The varnished paper may be prepared by half an ounce of mastic varnish and three ounces of spirits of turpentine, hung up to dry, and treated as the oiled paper in iodizing; but both are better for resting a short time previous to iodizing upon water containing a little isinglass in solution, but used very sparingly.
As I have experienced the excellence of these preparations, I hope they may be useful to your photographic students.
Weld Taylor.
Bayswater.
After-dilution of Solutions.—There are in general use two methods of preparing sensitive paper. In one, as in Mr. Talbot's, the iodide of silver is formed in a state of purity, before being rendered sensitive: and as, for this end, a small quantity only of nitrate of silver is necessary, a very dilute solution will answer the purpose as well, or even better, than a strong one; but by the other method, the paper being prepared with iodide of potassium only, or with some other analogous salt, the iodide of silver has to be formed by the same solution that renders it sensitive. Now as for every 166.3 parts of iodide of potassium 170.1 parts of nitrate of silver are required for this purpose, it is evident that a dilute solution could not be employed unless a very large bulk were taken, and the paper kept in a considerable time.
The after-washing is to remove from the surface of the paper the great excess of silver, which is of but little service, and prevents the paper from keeping.