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The photographic news
- Bandzählung
- 6.1862
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- 1862
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 189, April 17, 1862
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Zeitschrift
The photographic news
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Band 6.1862
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- Register Index 619
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Band 6.1862
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[APRIL 17, 186- 188 THE PHOTOGRAPHIC NEWS. Continent, have pointed out the fact, that the use of hot.d loping solutions permitted a considerable shortening of tin; posure in collodio-albumen plates. Moro recently stila Draper and others, in America, state that good pictures» been obtained on ordinary tannin plates, by an exposure of or three seconds, when heat has been used in develop® whereas the same plates required an exposure of an equal nu. of minutes when the ordinai-y processes of developing " adopted. These facts are important and interesting, but they ref the verification of successful repetition in this country. . shall refer to this subject in our next, when we hope to bo 9 to state the results of some experiments. ing of glycerine and water. When about to be intensified, it is well washed and flooded with a solution of iodine and iodide of potassium, about two grains of each, in water; this is washed off in a few minutes, and a solution of pyrogallic acid, with a little silver added, is applied to the plate until the right intensity is obtained. Both Mr. England and Mr. Blanchard, unlike Mr. Wilson, use portrait combinations for producing their instantaneous views, and each use lenses of different focal length and diffe rent stops for different subjects. In street views the curvature of field incident to combinations of lenses does not become a serious evil: we believe, however, that the rapid portrait lenses recently made by some of our best opticians give a flatness of field not to be exceeded by single lenses. Where from the nature of the subject, and the the amount of light, view lenses can be used for landscape work, they will doubtless be pre ferable ; but as in instantaneous work rapidity of action is the first consideration, there can be no question as to the superi ority of combinations for many purposes. The modes proposed of uncovering and covering the lens to obtain the minimum of exposure are various, each operator having some favourite method. Mr. Wilson frequently uses his Scotch cap, moving it off the lens and on again as rapidly as possible. Sir.England’s clever contrivance, describedin another page, seems as perfect in principle as it is found efficient in practice. Mr. Blanchard’s practice is similar in principle to that of Mr. Wilson, only he uses a piece of wood with a ledge to rest upon the lenses, instead of the Scotch cap. We have seen other impromptu contrivances of the same kind made to answer the purpose perfectly ; the argument in their favour is, that any thing so under the control of the operator gives him more lati tude in varying the rapidity of the exposure with the character of the subject than any contrivance depending upon the action of a spring or its own momentum no matter how acquired. The general conclusion to be deduced, then, from the prac tice of professional instantaneous photographers, appears to point out highly bromized collodion and strong iron-developing solution, in conjunction with a nitrate bath of pure silver as nearly neutral as possible, together with good lenses and good light, as the necessary agents in producing instantaneous pic tures. We have before us a series of examples of the instantaneous productions of other professional and amateur photographers, together with statements of the formula) and manipulations used; but we have thought it desirable rather to refer to pic tures with which the public is familiar, and afford an opportu nity of comparing processes with published results. In the majority of instances, however, we find, when the proportions of the sensitizing salts are given, that from one-third to an equal quantity of a bromide is added with the iodide, and that the salts of cadmium are generally preferred. In some in stances the collodion of different commercial manufactures is quoted, and in these cases we find that those collodions which have the reputation of containing cadmium, and containing bromides, are generally referred to; and also that it is a very common circumstance to find that a mixture of the collodions of two different makers is found better than either singly. It must not be forgotten that in instantaneous photography pre eminently, the best chemicals, the best formula, and the best apparatus, will be of little avail, without great judgment, skill, ami care at every stage of the operations. This hasty sketch of the rapid processes in use would be very incomplete without some reference to the rapid dry processes at present exciting public attention. We notice in another page some instantaneous views taken on dry plates prepared by Dr. Hill Norris. This process is, unfortunately, a secret one, and as such scarcely of legitimate interest for discussion in our pages. There are two facts in regard to them of which, how ever, wo are in a position to speak with certainty, the informa tion having been derived directly from Dr. Hill Norris himself. These facts are, that they are not prepared with a simply iodized collodion ; and that their sensitiveness does not depend on the presence of free nitrate of silver, as every effort is made by washing to remove every trace of a soluble salt of silver from the film. Mr. England has by his process, he states, prepared dry plates which equal in sensitiveness ordinary iodized collo dion when developed by pyrogallic acid. But the chief source of rapidity to which attention has recently been directed is the aid of heat in developing. Old photographers remember that many years ago Ferrier, Martin, and others, used hot.solutions of gallic and pyrogallic acid for developing albumen plates. Mr. Mudd in this country, and more recently M. Homan on the * Read before the American I Photographical Society Monday e Feb. 10th, 1862. MATERIALS FOR SILVER BATHS. BY NICHOLAS PIKE.* Within the past year quite a number of articles have V contributed to the photographic journals published in' city, on the peculiar merits of the recently introdo wooden baths the holding nitrate of silver solution/ photographic purpose. These articles are, in my epi®' likely to lead the professional community, and more 6 cially those who are living in the rural districts, in* 0 error. For some time past I have experimented with 1‘ different materials in constructing baths for holding si solution, and particularly with wood. It is well known that by a careful examination of a section of any kind of wood, with a good microscop” reveals to us at once that it is not solid, but composed*] vast number of small tubes ramifying through every E and even the oldest and most compact species are notl more than a collection of vessels and cells, which consis* extremely thin and delicate membranes. In selecting s f“ mens for my experiments, I examined, microscopic more than thirty different kinds of wood in order to 1) use of those which were most compact and which conts the most minute vessels and cells. The baths were carefully made, and a good coatib5, shellac was used inside, but in every instance in a few mo the silver solution became injured by the decompositio the shellac, which would crack and peel off. This de” position would be more rapid when the solution was slig), acid. In a large bath which was in use about ten month* 1 ! shellac was completely dissolved away, and the silver sol®, permeated the wood in such a manner that I recovered • ounces of metallic silver on reducing it to ashes ; andl the bottom of another bath which only measured four* inches in length, by two in width, and one in thickne, recovered one ounce and eleven grains. The solution 3 remained in this bath undisturbed for sixteen months. ] sides and ends I have not yet examined chemically, bull sure they are rich in silver, as a microscopic examinati a longitudinal section reveals the fact that the meduh system is completely filled with the precious metal. A solution has permeated every part and has crystallised the outside. My next experiments were with the common poro bath, such as are usually sold by the trade. I have three or four of these baths filled with silver for th® < three years, and in every instance I have found thel absorb and injure the solution. After they have be use ten or twelve months the glazing begins to crack . owing to their porous nature the solution permeates thrl and crystallises on the outside, and in a snort time the. becomes completely saturated. From a bath of this 5 which Mr. Davis, of Brooklyn, had in use, 1 took sixta grains of metallic silver which had formed on the outs1d the short space of twelve hours. I reduced this bats powder, and from a small portion I extracted one ouncs twenty-three grains of pure silver, and I have not the doubt that from the balance I shall procure two OLD Ar ounce: the fit for eit This j of a si Ih a con Mend time; soon laid I made this < and . It is, genei 'They many only of ba to pl The Colle F.S T1 eonf the ‘ N Pell thin as v Cole & case wen fact; ing adm M mur Exh rest ven far ope: exa Pe Sim mig Kir reci Sin I Ph: wa pre du Ti Tl as to pa in in re cl It P<
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