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862. 1 we see anyway house in rey, Rey- •it ly, so far The thin ig in such er foot we r columns Amateur . 4. The “twin,” lar mate- er would tampton." intensity, em would ion giving Che prints antprints a little ies from he sitter) thelighl y marked .ring e 111 ' negative ition, b" imperfed y lighted c shadin: protect t l give such hould loper. 3 re such* light a> rest need will need card por- •face ren- ver tone ight. . ich omis t it, how- i suggest, anders o stion did it journal s without is created I it real? litedtho ave sin* ■ referred ther r tse mad’ herpo is ont langer tunate ankyd" det,” into li 1 ' m W' :eof* xposure longer in you’ vou no" corted reen 20 spec* eguire, nralebi ens,a0d V Of ^Unless vaclcar ■s in the ones > n 1 is To gbt, for e irW“ ioedol Is ine Id pro- THE PHOTOGRAPHIC NEWS. Vol. VI. No. 208.—August 29, 1862. MR. PONTING ON INSTANTANEOUS PICTURES* Is the period when success in photography was considered to be largely due to the possession of secret formul, it used to be a common remark with a celebrated Daguerreotypist, as a reason for avoiding conversation on his art, that “ it was impossible to talk long upon a subject without saying iomething.” In a work on the collodion process, by the manufacturer of a collodion of high reputation, but unknown constitution, it will naturally be expected that some part of the secret would ooze out. This secret has been the subject of much speculation and some investigation. One experi mentalist evaporates the iodizing solution, and submitting the residue to microscopic examination, finds certain plumose Crystals, which do not answer to the characteristics of any iodide he knows. Another, proceeding, chemically, applies the reagents for cadmium, and is satisfied from the result that the iodide of cadmium is used. Another examines and states that he finds cadmium and calcium. Still, amongst amateurs and manufacturers the matter remains undecided. Mr. Ponting has shown that it was quite possible to write 1 Useful book without divulging his secret, or saying much about the manufacture of his collodion. He has, however, mid something, and we learn either from direct statement, J r by implication, that it contains an iodide only, and no bromide ; that the iodide is not, or at least not entirely, that of cadmium, and that it contains equal proportions of ether and alcohol. Beyond this, nothing is divulged as to the constitution of the iodized collodion, which has long held snch a reputation for sensitiveness and stability. On the working of this collodion, and other photographic Operations, there is, however, much valuable information, he details of some experiments on the influence of acetate 0 silver in the nitrate bath, are very interesting, and well "orthy of attention. We shall refer to this and some other Parts of the book on a future occasion. » Our especial object at present is to call attention to Mr. .eating’s observations on instantaneous photography, a "ranch of the art which is of very absorbing interest to most "otographers at the present time. It is very satisfactory as to find that a gentleman who has so long and so suc- mrfully manufactured a simply iodized collodion, has, from j r recent experience, arrived at a conviction which con- n‘ns the position we have always steadily maintained, lemtely, that a bromide properly used is essentially an acce- hnttor, and that its use is imperative in instantaneous ope- 10 ns. Referring to recent discussions on the subject, he "This alleged fact of bromine being an accelerator en ite contrary to my own previous experience, for, in all aP timents with this material, 1 found that it not only re- ed the action, but produced a thin weak negative.” A ofisof .careful experments were instituted, the issue of wich 13 aconviction thus expressed : “ These experiments, demn have since been fully confirmed in practice, clearly Hof 0 ] rate that for instantaneous pictures, it is necessary portin v to’use bromide in the collodion, but a small pro- exgperin of nitric acid in the bath.” A careful detail of the wments referred to is given, which we subjoin :— Xo, 18 samples of collodion were prepared as follows:— ‘ Odlized Collodion, containing 4 grs. of iodide to the oz. R’surehptorraphic Dimiculties ; How to Surmount them : Instantaneous “Co, " to obtain them.” By T. C.u>by POXTINC. London : Bland No. 2, the same Iodized Collodion, with } No. 3, ditto ditto „ 1 No. 4, ditto ditto „ 2 No. 5, ditto ditto „ 4 gr. of bromide added. „ ditto „ ditto „ ditto. “ Three nitrate of silver baths were also prepared, of the strength of 30 grains to the ounce. “No. 1. This bath was made according to the formula at page 22, with acetate of soda and acetic acid. “ No. 2. To this bath was added a quarter of a drop of nitric acid to each ounce. “ No. 3. This was left neutral, or nearly so, having a very minute proportion of acetic acid to prevent fogging. “ The developer was made with— Protosulphate of iron 10 grains Glacial acetic acid .. 6 drops Water ... ... ... ... ... 1 ounce. “ Two negatives were taken with each sample of collodion, one exposed two seconds, and the other four seconds, in the three baths in succession, being thirty negatives in all. A land scape lens with a small stop was used, in order to secure com plete accuracy and uniformity in time of exposure, which it would have been difficult to obtain with so many negatives, had a shorter exposure been tried. “ Without wearying the reader with a detailed account of all the negatives, it will suffice briefly to state the results that came out. “ First, as to the baths. With the ordinary iodized collodion No. 1, the bath No. 1, with acetate of soda and acetic acid, was unmistakably the quickest of the three, the nitric acid bath, No. 2, being very slow; this, it will be remembered, is the precise results of the experiments detailed at page 19, except that a bath with nitric acid was not then tried. But with the collo dions containing bromide, the No. 2 bath with nitric acid proved to be much quicker than the other two baths, their slowness as compared with the nitric bath increasing as the proportion of bromide in the collodion increased. No increase of sensitive ness was gained by the large doses of bromide; on the contrary, the collodion No. 5, with four grains of bromide per ounce, worked much slower than either of the other samples. The proportion of one grain of bromide to four grains of iodide, gave the best results, larger doses of bromide imparted a wavy ap pearance to the film that quite spoiled the picture, and no in crease of sensitiveness was obtained. “ On comparing the negative taken with the No. 1, on iodized collodion, in the bath No. 1, with the negative taken with bromo iodized collodion, in the nitric acid bath, the latter was mark edly the better. The first was a very intense negative, with strong contrasts of light and shadow, and would have printed hard ; the latter was a soft, though a sufficiently forcible nega tive, giving full details in the shadows, and hardly wanted further development; but, with instantaneous pictures, the de velopment will have to be continued by using a weak solution of pyrogallic acid, with a little silver added, say Pyrogallic acid 1 grain Glacial acetic acid 6 drops Water 1 ounce. Solution of nitrate of silver (strength, 50 grains to the ounce), five or six drops, or more if great intensity be required. The iron developer must be previously washed off. “ These experiments, which have since been fully confirmed in practice, clearly demonstrate that for instantaneous pictures, it is necessary not only to use bromide in the collodion, but a small proportion of nitric acid in the bath ; these, with an iron developer as strong as the operator can use, as described at page 30, strengthening by the use of the pyrogallic developer, is all that is requisite in the way of chemicals. But it must be borne in mind that everything must be of the highest degree of purity, and prepared with the utmost care.”
