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The photographic news
- Bandzählung
- 12.1868
- Erscheinungsdatum
- 1868
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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. 502, April 17, 1868
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Zeitschrift
The photographic news
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Band
Band 12.1868
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- Titelblatt Titelblatt I
- Kapitel Preface III
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- Register The Index To Volume XII 619
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182 THE PHOTOGRAPHIC NEWS. [APRIL 17, 1868. of working with certainty of cleanliness in an absolutely neutral or slightly alkaline bath is in itself a power which promises a long train of advantages of which photographers will gladly avail themselves. The immunity from the most fertile source of pinholes, the gradual accumulation of iodide of silver in the bath, is an advantage that does not require affirming. We just briefly glance, in passing, at two of the features of a system of working in regard to which its author pro mises, on occasion of fuller explanation, to point out variously ramifying advantages. Our immediate aim is to give as clear a resume as wo can, briefly, of the operations already stated. Mr. McLachlan commences with a denial of a generally accepted proposition, namely, that a pure neutral solution of nitrate of silver is not altered by light. Although not apparently changed by light, he states that after exposure it has acquired new properties. He dissolves nitrate of silver, by preference of a given quality described on another page, at the rate of one ounce in an ounce of distilled water, and exposes it to the action of light; the longer the time and the more sunny theweather the more perfect the result; but at least a month of summer weather is desirable. The proof of new propertiesacquired is thus made :—To an ounce of the solution, unsunned, add one drop of a solution of caustic potash containing one grain to the ounce ; the result will be the production of turbidity from the precipitation of oxide of silver. Now add a drop of the potash-water to the sunned silver solution, and whilst oxide of silver is formed it is at once redissolved. A considerable amount of the potash solution may be added, Mr. McLachlan states, to a thoroughly sunned bath, and the oxide of silver will be re dissolved as rapidly as it formed. This capacity for holding oxide of silver in solution, and preventing its precipitation, is the source of cleanliness and freedom from fog in using an alkaline bath. After sunning the strong silver solution, to 1 ounce of which 1 grain of the potash solution has been added, 2 grains of iodide of potassinm dissolved in a few drops of water are added to 10 or 12 drops of the strong silver solution, and the iodide of silver formed is, after washing, added to 1 ounce of the strong silver solution, by which it is, of course, at once dissolved. Pure distilled water to dilute the solution to a strength of 35 grains to the ounce is now added, and this causes no precipitation of iodide of silver, and the bath may be used at once; but in the course of four or five days another singular property acquired by the silver solution is manifested : a sudden precipitation of iodide of silver takes place, and the solution, according to Mr. McLachlan, has lost the power of dissolving or precipitating any more of this salt. No addition of water produces turbidity or causes further precipitate of iodide ; and, in the course of use, no further accumulation apparently takes place, or, at least, no manifestation of its presence in the shape of pinholes. Then a suitable collodion is required, for Mr. Melachlan lays great stress on the importance of harmonious relation of the various chemicals. At a future time he will explain the manufacture of suitable collodion ; but for the present explains the doctoring of a commercial sample. Take a good commercial sample of a certain type—Mawson’s is selected as the illustration—in a red acid condition, such as ordinarily secures brilliant and clean negatives. A plate coated with this, and immersed in this alkaline bath, will give inevitable streaks, brain-markings, and other troubles. To get rid of these the collodion must be made neutral by adding a few drops of the potash solution, and, after this treatment, the neutral collodion in the alkaline bath will give a clean brilliant negative—delicate, harmonious, and well modelled, with a shorter exposure than is obtained by the usual mode of working. For a special mode of preparing the developer, we refer the reader to the report of Mr. McLachlan’s remarks on another page, and for fuller elucidation of his system of working they must await his further communication. It is probable that Mr. McLachlan might have done him self and his method more justice by a written communica tion, as nothing enforces precision and the absence of redundancy more certainly than the necessity of writing. As the matter stands, he has afforded sufficient information to excite expectation and stimulate experiment, after which a fuller written paper will be received with greater interest and fuller appreciation. MR. WOODBURY'S PHOTO-RELIEF PROCESS. When an important discovery is made it is scarcely sur prising that many claimants for the honour and possible profits of its paternity should start up, as the vanity, cupidity, and capacity for self-deception which exist in the world are prolific parents of such claims. But it is not a little surprising to find, in addition to these, other claim ants perversely created by the carelessness or misconceptions of the recognized recorders of progress in the periodical press. We are not aware, for instance, that M. Braun has ever claimed for himself the discovery of Mr. Swan’s carbon process; but we have had very repeatedly to point out for correction erroneous claims made for him by journals which ought to have been better informed. A similar error is made in the April number of our excel lent monthly contemporary, the Art Journal, in which an article is devoted to the description of a method of printing, headed “ M. Disderi's Patent.” The process is really that well known to photographers as Mr. Woodbury’s photo relief process, an example of which was placed before our readers a couple of years ago, the English patent of which was recently sold by Mr. Woodbury to a company', of which M. Disderi is managing director. The process is mentioned, however, throughout as “ M. Disderi’s method,” and only by a passing allusion at the end of the article is any recognition made of the actual originator of this mode of printing. “ The peculiarity on which the patent is based is the inven tion of Mr. Walter Woodbury,” it is stated, and the con clusion to which the whole article points, and which, if it be not contradicted, it may be hereafter quoted to prove, is that M. Disderi has patented a new process based upon the relief process of Mr. Woodbury. The simple fact is, that the process which has been put into operation with so muc energy and success by M. Disderi is that which has been worked out in its minutest details to its present state of per fection solely by Mr. Woodbury, and the origin of which has never been claimed by M. Disderi. We have pleasure in noting here that the commercial working out of the process under M. Disderi’s superinten dence at the establishment at Brompton appears to progress very successfully. The minor difficulties attendant upon working out, on a large scale, a mode of printing based upon new principles and involving many new conditions have gradually disappeared, and excellent pictures on glass and paper are now regularly produced, whilst the sales and orders are already in excess of the supply. Mr. Woodbury, who has recently been on a business tour on the Continent, has made arrangements which will speedily introduce his process into Italy, and also established negoci- ations which will probably be speedily followed by its intro duction into Austria and Bavaria. The enterprizing firm of Goupil and Co., so well known in connection with the extensive publication of engravings and of photographic art reproductions, are rapidly making arrangements for work ing the French patent on a largo scale ; and Mr. Woodbury shortly leaves for the United States to take the proper stops for initiating commercial operations with the process under the auspices of a powerful company in America. A MAN’S PROPERTY IN HIS OWN PORTRAIT. A few years ago an American paper contained an advertise ment from a murderer under sentence of death, warning the public that a certain photograph of him, recently published,
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