Mr. Hunt, quoting, (apparently with approbation) from Mr. Archer, says (p. 260., 3rd edit.), "Take one ounce by measure of nitric acid, mixed with one ounce by measure of ordinary sulphuric acid, and add to them eighty grains of cotton; well stir," &c., "for not more than FIFTEEN SECONDS," &c. "It will be seen that the cotton is not exposed to the action of the mixed acids in this last mode longer than is necessary to saturate the cotton; should the action be continued further, the solubility of the cotton is entirely lost."
Not only is the order of manipulation different (a point probably not material), but the time between "five minutes" and "fifteen seconds" must exercise a most important influence on the result. Who is right?
Cokely.
Sealing-wax for Baths.—I notice in your answers to correspondents (No. 176., p. 274.), that you inform H. Henderson that glass may be cemented for baths with sealing-wax. May I recommend to H. Henderson the use of gutta percha, instead of glass, for that purpose? Sheet gutta percha is now very cheap, and the baths are most easily made. I have had one of my own making in constant use since last July, having never emptied it but twice, to filter the nitrate of silver solution. It is not liable to breakage. The joinings are much less liable to leakage. And when it is necessary to heat slightly the silver solution (as it has been during the late cold weather), I have adopted the following simple plan: Heat moderately a stout piece of plate glass; plunge it into the bath; repeat the operation according to the size of bath. It is very useful to make a gutta percha cap to cover over the bath when not in use; it protects it from dust and evaporation, and saves the continual loss of materials arising from pouring the solution backwards and forwards. For home-work I have reduced
the whole operation to a very simple system. My bath, hypo-soda, developing fluid (of which, as it keeps so long, I make ten ounces at a time), are always ready in a small closet in my study. These I arrange on my study-table: a gutta percha tray, a brass levelling-stand upon it, a jug of soft water, and half-a-dozen small plates to place my pictures on, after treating them with the hypo-solution (for, to save time, I do not finish washing them until I have done all the pictures I require). All these things I can prepare and arrange in less than ten minutes, and can as easily return them to their places afterwards.
With regard to Mr. Mabley's process, described in "N. & Q.," No. 176., p. 267., as I am but a beginner myself, and have much to learn, I should be sorry to condemn it; but I should fear that his pictures would not exhibit sufficient contrast in the tints. Nor do I see the advantage the pictures would possess, if they did, over positives taken by our process. We amateurs in the country labour at present under great disadvantages, some of which I think the Photographic Society will remove. I am myself quite unable to form an idea what the collodion pictures done by first-rate photographers are like. All the positives done by amateurs in this part of the world, and developed by pyrogallic acid, which I have seen, present a dirty brown hue, by no means pleasing or artistic; and I have seen but very few, either developed by pyrogallic acid or protosulphate of iron, free from blemishes. I think if we were to act upon the suggestion made in "N. & Q." some time back, and send the editor a specimen of our performances, it would be a slight return for his endeavours in our behalf; and he would, I doubt not, honestly tell us whether our pictures were tolerable or not. I, for one, shall be very happy to do so.
J. L. Sisson.
Edingthorpe Rectory.
Developing Chamber.—I think Mr. Sisson will find some difficulty in applying his very excellent idea of a sheet India rubber lighting medium to his portable laboratory, as the vapour of the ether will act upon it and render it sticky and useless after one or two usings. Allow me to suggest what I am in the habit of using, viz. a double layer of yellow glazed calico, stuck together with a little common drying oil, and allowed to dry for a few days: this causes a perfect exclusion of the actinic rays, and is very durable.
F. Maxwell Lyte.