PHOTOGRAPHIC NOTES AND QUERIES.
Photographic Notes.—G. H. P. has communicated (Vol. vii., p. 186.) a very excellent paper in reference to our numerous failures in the collodion process; but the remedies he proposes are not, as he is aware, infallible. He gives the recommendation you find in every work on the subject, viz. to lift the plate up and down in the bath to allow evaporation of ether. I have made experiments day after day to ascertain the value of this advice, and I am convinced, as far as my practice goes, that you gain nothing by it; indeed, I am sure that I much oftener get a more even film when the plate is left in the bath for about two minutes without lifting it out. I should be glad of other photographers' opinion on the point.
I have never found any benefit, but much the contrary, from re-dipping the plate in the bath; and I may observe the same of mixing a drop or two of silver solution with the developing fluid.
I think with G. H. P. that the developing solution should be weak for positives.
I omitted, in my description of a new head-rest, to say that it is better to have all the parts in metal; and that the hole, through which the arm runs, should be a square mortice instead of a round one, as is usual. A screw at the side sets it fast; the lower portion of the upright piece being round, and sliding up and down in a tube of metal, as it does in the best rests, allowing the sitter to be placed in different positions. All this is very difficult to describe, but a slight diagram would explain it easily, which I would willingly, as I have before said, send to any one thinking it worth writing to me for.
J. L. Sisson.
Edingthorpe Rectory.
On some Difficulties in Photographic Practice.—Being desirous to have a glass bath for the silver, I was glad to find you had given (in "Notices to Correspondents") directions for making one, viz. two parts best red sealing-wax to one part of Jeffries' marine glue. I tried this, but found the application of it to the glass impossible, as it set immediately. Now, can you afford room for the means by which this may be remedied; as my wish to substitute glass for gutta percha remains?
Now I am addressing you, may I offer one or two hints which may be of service to beginners? If, after what has been considered a sufficient washing of the glass, after the hypo., during the drying, crystals from hypo. remaining appear, and which would most certainly destroy the picture, I have found that by breathing well over these parts, and immediately repeating the washing, all ill effects are thoroughly prevented. To substitute hot water instead of breathing does not destroy the hyposulphite, and therefore will not do.
When the plate shall be dry after the washing process, if a leaden, dim, grey appearance occurs, I have found that by tenderly rubbing it with fine cotton, and applying with a good-sized camel's hair pencil a varnish of about 8-10ths spirits of turpentine and 2-10ths mastic varnish, and then, before this gets dry, putting on the black varnish, the grey effect will have been removed.
I have found the protonitrate of iron, as also the protosulphate, and not seldom the pyrogallic, so difficult of application, that I have stained and spoiled very good pictures. I have therefore used, and with perfect success, a tray of gutta percha a little longer than the glass (say one-fourth of an inch), and one-fourth of an inch deep; sliding from one end the glass into the tray (supplied immediately before using it), by which means the glass is all covered at once.
I think the Rev. Mr. Sisson's suggestion, viz. to send you some of our specimens with collodion, a very proper one, if not declined on your own part, and shall, for one, feel great pleasure in acting in accordance with it.
You will, I trust, pardon any foregoing hints for beginners, as I well know that I have lost several pictures by hypo-crystals, and very many by the difficulty in developing.
L. Merritt.
Maidstone.
P.S.—I always find collodion by Dr. Diamond's formula capital, and with it from five to ten seconds is time enough.
Mr. Weld Taylor's cheap Iodizing Process.—I have no doubt Mr. Weld Taylor will be kind enough to explain to me two difficulties I find in his cheap iodizing process for paper.
In the first place, whence arises the caustic condition of his solution, unless it be through the decomposition of the cyanide of potassium which is sometimes added? and if such caustic condition exists, does it not cause a deposition of oxide of silver together with the iodide, thereby embrowning the paper?
Why does the caustic condition of the solution require a larger dose of nitrate of silver, and does not this larger quantity of nitrate of silver more than outbalance the difference between the new process and the old, as regards price? I pay 1s. 3d. for an ounce of iodide of potassium of purest quality; the commoner commercial quality is cheaper.
F. Maxwell Lyte.