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The photographic news
- Bandzählung
- 6.1862
- Erscheinungsdatum
- 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. 220, November 21, 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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November 21, 1862.] concerning the results derived from the above described solutions, but at the same time he over estimates the decom posing power of his hot water. In beakers 1, 2, and 3, the quantity of gold is precisely the same, consequently the same amount of chlorine is driven off by the heat applied, and for some little time the atmosphere receives the whole, for water, when its temperature is raised much above 60°, cannot hold in solution the above-named gas, but when the several solutions are diluted, evaporation ceases, and a natural toning action begins. In beaker No. 1, the quantity of soda present is not proportionate to the amount of chlorine the gold still holds in combination, and for reasons given in my former letters, unsatisfactory toning is the result. In No. 3. the case is different, the soda and gold is nicely balanced, and an advantage is gained by the reduced quantity of chlorine, as in all probability a deeper deposit of gold is secured, and consequently a greater depth of colour is ob tained. And now, bidding farewell to Mr. Elliot, who I hope will forgive the liberty I have taken, and accept my criticism on the contents of his paper in the same spirit in which they are offered, I propose, in conclusion, venturing a word or two on theable and well studied subject advanced in your last number by E. E. L. : he has started an interesting question respecting the agency employed in the production of the varied colours yielded under the influence of toning action. Now the first question which naturally suggests itself is the enquiry, what is colour ? Considered in bodies, it is a sensation produced on our visual organs, by a decomposition of light produced by reflection and absorption, and the diversity of colours proceeds from the varying disposition of bodies to reflect light, so that any alteration in the molecular arrangements of a body, will modify, or completely change its colour, by absorbing or reflecting additional rays of light; in con sidering the various colours produced by the same toning bath, we must not overlook the fact, that, the surface on which the gold is deposited, is of an ever-changing nature. The subtle agent that reduces by its electric influence, the chloride of silver, is seldom long existing in the same mood, its changes are as frequent and directly, more plainly visible, than its effects on the surface of the paper, than the changes that are ever present in the operating department. To day vigorous prints arc produced, giving, when toned, a fine dark and brilliant colour* To morrow, under appar- antly the same treatment and conditions, the prints are brown, giving depth of printing reduction, without a vigorous appearance, these prints, when exposed to toning action weaken, and if pressed for dark tones, give slatiness. I have noticed those changes in one day, and with one batch of prints—more especially at this season of the year—the early morning seldom yielding the same class of prints as at mid-day ; the ever varying character of the negatives will also exercise an influence on the reduced silver surface ; the light being strained through these, ere it reaches the paper, many modifications of its action must ensue, from the pecu liarities of each negative, and as many changes must be effected in the molecular arrangements of the reduced silver; in one, the requisite conditions are present to aid in giving opacity to the coating of gold ; in another, the conditions are such, that its surface is too transparent to admit of a deep colour, and an attempt to procure it by toning is altogether useless, for by another molecular arrangement, slatiness becomes visible, and the print spoiled. I fain would go fully into this subject, but fearing I have too long trespassed on your space, I will forego the temptation.—Yours, respect fully, A Photo’s Assistant. Aqotographir states an Quexies. THE Invention OF Photolitiiograpiit. Sin,—As the question of who first invented photolithography seems to bo interesting tho public at present, allow mo, as the * I am here speaking of portraiture. party entrusted with the working out of that known as Col. Sir H. James’s photozincographic process, to say a few words on the subject. Photozincography is a working out and application of the theory set forth by Asser and others. My first experiments were printing in carbon on paper prepared with carbonate of potash and gum, gelatine or albumen, for tho purpose of trans ferring to the waxed surface of a copper plate, as a guide to the engraver. Finding that the carbon print, when transferred, gave too faint an impression, it was thought that printing-ink would be a suitable material, which was tried and found to succeed very well. It then occurred that these prints could transfer equally well to zinc or stone ; this also proved success ful, and was the way that tho discovery of photozincography was made at the Ordnance Survey Office. The experiments were first made in the autumn of 1859, at about the same time as Mr. Osborne was at work in the same direction in Australia. Col. Sir H. James first published this process in his report to Parliament for 1859, and did not annouince it in tho Photo graphic News until March 1860, so you will perceive that England was not behind her colonies in bringing out this new art.—I am sir, your obedient servant, ARCHD. J. Bider. P. S. As the application of photolithography commercially seems to be little known to the public, I shall be glad to send you shortly some specimens of valuable and rare reproductions, which I and my partner, Mr. Preston, are at present engaged with. [This letter was omitted in our last through an oversight in “ making up” the formes. We have since received tho follow ing satisfactory and explicit letter, to which we have pleasure in giving publicity. The mention of exact dates in such matters is always desirable. Wo are glad to record Mr. Rider’s initiatory steps, and also Col. James’s recognition of them. It so happens, that in the co-operative labours carried on in a large military establishment, honours as well as labours are divided, the chief honour culminating in the chief officer, as leading, guiding, permitting, or controlling the whole. We now append the second letter.—Ed.] Sir,—In an article in last week’s News, on " Photozinco graphy, Photolithography, and Photo-engraving—Who are the Discoverers?” you refer to a letter from me, claiming a share in the invention of Col. Sir H. James’s process; ami, as you say it is scarcely sufficiently definite, perhaps you will allow me to state a little more fully in what way I am connected with it. In the autumn of 1859 (I cannot give tho date), being then engaged in tho photographic department of tho Ordnance Survey Office, I was ordered to prepare some carbon prints of reduced maps, with tho view of transferring them to copper. Tho process used was that published by Mr. Pouncy, the paper being coated with a mixture of gum, bichromate of potash, and carbon; the results were not very satisfactory, as very little of the carbon could be made to adhere to the waxed sur face of the copper. Seeing a description of a carbon print ing process by M. Asser, in tho News, of November 25th, 1859, I tried it, but did not get very good results, as I found it very difficult to make the ink adhere to the insoluble parts of the paper while in a moistened state. I next tried the appli cation of the ink before fixing, and in this was successful. Gum and bichromate were first used, but in course of practice gelatine was found to answer better. After producing a transfer by this method, I showed it to Sir H. James, who then ordered me to copy a small etching and make a transfer, which was transferred to zinc and printed. In the pamphlet just published, Sir H. James, in his intro duction, gives a history of the process, but has omitted to men tion ray name in connection with it; but if you refer to his Parliamentary Report for 1859, you will find he names mo as having introduced something new: also, in his letter to the News, of March 16th, 1860, speaking of the process, ho says: “With the aid of Mr. Appel, who is so well-known for his skill in zincography, and with the assistance of Corporal Rider, R.E., who is one of our photographers, we have, I think, perfectly succeeded, our success being duo to the fact, that wo have in this establishment both first-rate photogra phers and first-rate zincographers, although I am myself neither tho one nor tho other.” Again, speaking of (ho inven tion in tho introduction to the/ac iimiles of “ Domesday Book,” which were published before my leaving, ho says to Captain
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