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THE PHOTOGRAPHIC NEWS. Vol. VII. No. ^.—OctoLer 30,1863. CONTENTS. Strength of the Printing Bath 517 -1 it ical Notices—A Systematic Handbook, &c.—Album Photo- graphs.—Photographic Illustrations.—A Group of Photo graphic Engineers and Opticians. — Stereographs of the English Lake Scenery 518 Jottings from the Note-Book of a ,l Photographer’s Assistant.” No. V 519 Rapid Testing of Collodion. By M. Me. A. Gaudin 520 Nitrate of Ammonia. By Carl Meinerth 520 On the Behaviour of Chloride, Bromide, and Iodide of Silver in the Light, &c. By Hermann Vogel. 521 Recent Patents 523 Analysis of the Silver Solutions used in Photography. By Francis Sutton 523 Proceedings of Societies—North London Photographic Assoc.... 524 Correspondence—Foreign Science—Photography in Colours— Cheap Battery for the Electric Light 525 Photographic Notes and Queries—Fraudulent Chloride of Gold —Perambulator Tent 526 Talk in the Studio 527 To Correspondents 528 Photographs Registered during the past Week 528 STRENGTH OF THE PRINTING BATH. Tuere is no subject of greater importance to the photo- • grapher than the proper strength of the silver solution used s in printing. There arc two aspects in which the question ) claims attention—the artistic and the economic. It is of 1 primary importance that the best results possible from the 1 negative should be secured ; and it is necessary that these results should be obtained at the least possible waste of the । precious metal. Perfect results must not, in any degree, । be sacrificed to economy; but there should be no expen- ; diture which is not accounted for in the results obtained. The subject of the discussion at the last meeting of the North London Photographic Association is, therefore, worthy of a more extended and experimental attention. The question really resolves itself into this :—What is the minimum strength of silver bath with which the maximum of excellence in printing may be obtained? There arc three distinct operations to be performed by the nitrate bath in exciting al bumenized paper. It has to render insoluble, or “coagulate,” the albumen; to convert the soluble chloride combined with the albumen into chloride of silver, and to supply the requisite proportion of free nitrate of silver necessary to rapid and vigorous printing. Any strength of solution which performs these offices, or any of them, imperfectly, will yield bad prints, and fail in securing the primary end of printing. Any proportion of silver present more than is necessary for these ends is waste ful. and fails in securing the second condition, economy. The advocates of strong baths advance various reasons, many of which arc very cogent. First, in regard to the process termed “ coagulation,” they state that this, is rapidly performed before the water in which the silver is dissolved can exercise any solvent action on the albumen, whilst a weak solution attacks the albumen at once, ■ and dis solving part, not only robs the paper of some surface and brilliancy, but also rapidly contaminates the nitrate bath. That the strong bath converts all the chloride present into chloride of silver rapidly, and so requires a short floating, by which the sensitive salts are largely kept on the surface, and an important condition of brilliancy secured. That the proportion of free nitrate necessary for good results being an uncertain quantity, is at least made safe by the use of a strong bath. And finally, that practice demonstrates the advantages of a strong bath in prints of greater force and brilliancy than can be obtained by a weak solution. These are the chief argu ments they advance as to the value of strong baths in secu ring the first condition, good results ; and in regard to the second condition, economy, they urge that all the silver not actually used in producing the image may, by care, be re covered, if the various residues be properly preserved. The advocates of weaker solutions simply affirm the strong ones to be unnecessary, and therefore wasteful. That the albumen may be rendered insoluble by solutions of twenty or thirty grains to the ounce, instead of sixty, eighty, or a hundred grains. That the whole of the chloride may be converted into chloride of silver by a longer floating on tho weak solution, as easily as by a shorter floating on a strong solution. That the necessary proportion of free nitrate is sup plied by the weak solutions, and that practices demonstrate the sufficiency of the weaker solutions in all cases where paper and judgment are used. On the score of safety, the advocates of strong baths have doubtless the best of the argument; but if satisfactory con ditions can be defined, there is no need to go to an excess to secure safety. Strong solutions do unquestionably rapidly “ coagulate ” the albumen, and thus prevent any portion from being dissolved ; they also permit a short floating, and thus prevent the silver solution from soaking so com pletely into the paper. Whether this keeps the image so perfectly on the surface, as is sometimes imagined, we are not so sure. This, we conceive, is really more affected by tho mode in which the first preparation of the paper is managed, for if the chloride employed have sunken into the paper, it is quite certain that, however short the floating, the silver will follow it. If the paper be new, the size readily soluble, and the floating on the albumen not very rapidly and skilfully performed, the salt will penetrate into the body of the paper, and the silver will follow it, forming as much of chloride of silver in the paper as on its surface. If, on the other hand, a paper be used, the sized surface of which has become hard and firm by age, and if the albu- menizing be managed with the rapidity and skill which forms a good surface without allowing the solution to pene trate or soak into the body of the paper, then short floating on the silver bath, will preserve the sensitive coating entirely on the surface, and secure the desired object. The objection to long floating, mentioned by Mr. Shadbolt, is more important. He suggested that if the nitrate of silver soak into the paper and enter into combination with the size, a compound is formed which is difficult to eliminate, and conducive to decomposition and fading. The question as to the proportion of free nitrate necessary to good results is the most difficult to decide. Its exact office is not well understood. We know that nitrate of silver is not itself reduced by light, and that pure dry chloride of silver alone is insensitive to light; we know also that even when it is in combination with organic matter, if all free nitrate of silver be washed away, it darkens slowly under the action of light; and we know that chloride of silver, in the presence of free chlorine, is insensitive to light. If paper prepared with chloride of silver only, without free nitrate, be exposed to light, it darkens slowly; but as the chloride of silver is reduced by light to a metallic state, > chlorine is liberated ; so that, after the first action of light, we have chloride of silver and the presence of free chlorine, and consequently a delayed and imperfect action results. ; If free nitrate of silver be present, it is stated by some that the ; chlorine liberated, attacks the nitrate, and forms a fresh r supply of chloride of silver to add vigour to the image. If i this theory be correct, then the proportion of free nitrate