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The photographic news
- Bandzählung
- 7.1863
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- 1863
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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. 226, January 2, 1863
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Zeitschrift
The photographic news
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Band 7.1863
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- Register Index 619
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Band 7.1863
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10 THE PHOTOGRAPHIC NEWS. [January 2, 1863. with india-rubber. I discarded it, finding that I obtain better results with gutta-percha. Having rendered the paper waterproof, I iodize and excite. The two proofs which I enclose I have finished in a very short time. They print quickly. I have only washed them in several waters for the space of a quarter of an hour, that you may see if they undergo a change by light and moisture. You will kindly make some remarks about it in your next number, if space permits. I beg you to pardon this hurried note, having been in haste for the post. If you find the paper of any value, I will continue to experiment, and will send you, by your per mission, specimens. I beg you also to remark if it will in fringe Mr. Sutton’s patent-right.—Yours respectfully, ALEx. AnNSIIN. Ambleside, Dee. 22,1862. [Our correspondent is experimenting more especially in the direction of Mr. Cooper than Mr. Sutton. If we under stand him rightly, he proposes the use of gutta-percha or india-rubber in place of albumen; Mr. Sutton as a prepa ration for albumen, The prints enclosed are very pleasing, and we shall be glad to hear further from our correspondent. We do not think he is trenching at all on Mr. Sutton’s patent-right. See note to a preceding letter.—En.] BROMIDES IN COLLODION. DEAR Sib,—I beg to correct a few errors in my letter of the 26th of July, published in your issue of the 26th September, and 13th of October, 1862, just arrived. Page 467, column 1: “ But Mr. Blanchard’s experiments appear to have,” &c., should be, “ appear at first sight to have,” &c. Page 467, column 2 : “to solve the question of increase of sensitiveness,” &c., &c., and a third portion, “with iodide of cadmium, 3 grains,” &c., should be, “ with iodide of cadmium, 3 to 4 grains,” &c. Page 479, column 1: “ introducing cadmium as a com ponent of the iodiser, &c., and that inferiority increased with the increase of cadmium,” &c., should be, “ and that superi ority increased,” &c. I hope you will give me space to make some further re marks on the present subject, and to record in your journal also, in a comprehensive form, the manner of my experi ments. A.—Cadmium Iodized Collodion. Istly. Superior in durability and sensitiveness, and equal in chemical intensity, under iron development, to the same with pyro. 2ndly. Whether under iron or pyro development, su perior in durability, sensitiveness, and intensity, to any bromo-iodised collodion developed with iron or pyro—that superiority being reciprocally as the quantity of bromide present in the bromo-iodide. B.—Iodide of cadmium, 3 grains, iodide of ammonium, 1} grains, compared with iodide of cadmium, 3 to 4 grains, bromide of ammonium 1} to 2 grains, both under iron develop ment. The simply iodized collodion, superior in every re spect to the bromo-iodized, reciprocally as the quantity of bromide present in the latter. C.—The same with cadmium and potassium, but with somewhat modified results and proportions; for in the case of the bromo-iodized, there is the usual limit to the introduc tion of bromide, when of the potassium salt. D.—And in all cases of like combinations between cad mium and ammonium, or cadmium and potassium, whatever the proportions, provided that the cadmium salt did not fall below half the total quantity used, the simply iodized-collo- dion was: Istly, Superior in every way under iron, to the same under pyro development. 2ndly, Under pyro, superior to the corresponding bromo; under iron only, when the amount of bromide was large. 3rdly, Under iron, superior to the corresponding bromo ; under iron, reciprocally as the quantity of bromide present. Thus, the collodion, iodized only with cadmium, under iron development, stands first; and iodized collodion, with not less than half of cadmium in it, and with iron develop ment superior to itself when under pyro development. All these experiments, be it remembered, were made with one collodion, with a bath very slightly acid with nitric acid; developers, pyro and proto-acetate of iron. They were all conducted as carefully as possible, and the results recorded are those obtained from each collodion in its best serviceable condition, and this, a little reflection will show, can only be done by repeated simultaneous trials of all the collodions on one and the same subject every two or three days, or every day (the latter the best plan), taking the best results of each up to its deterioration, and over the whole period of experi ment (as the highest attainable excellence), for comparative tabulation. Only this method could enable me to tell, or rather ascer tain, which collodion stood the longest without deterioration, which gave the best detail, which the most vigorous in action, and which the most sensitive, &c. And this now brings me to record the result of other ex periments, not, like the last mentioned, exactly intended to show the comparative merits of iodides and bromides under iron or pyro development, but to define the quality of the salts best suited for any one sample of collodion which may be required for early use, or be available in its least service able condition within a given time. A universal iodiser, or one suited for all collodions of reputable manufacture, is compoundable of equal portions of cadmium and ammonium, or cadmium and potassium, pre ferring the former combinations from its greater durability and power of conferring intensity. From this, as a standing point, it is not difficult to determine, by a few trials, in re ducing one salt or the other, the iodiser best adapted for any collodions against the day of requirement, whenever that may be; and we can defer the day, or shorten the period of ripening, by the knowledge that we can confer keeping properties by increasing the. proportion of cadmium, or injure them by the augmentation of ammonium. The first defers the age of ripeness or sensitiveness, but gives it greater duration; the second accelerates the said age, but makes it temporary—the more temporary when the ammonium is used as a bromide instead of an iodide. And now, with this information, we may compare any number of collodions differently prepared and salted, whether only iodised or bromo-iodised, anil determine the degree of their respective nature, properties of sensitiveness, durability, density &c., and cultivate any one or two, or all of these properties in the subsequent manufacture of other collodions, when intended to be particularly salted, which is probably the plan followed by most manufacturers. If, however, with such different samples of collodion, salted so as to put them in the best serviceable condition against a certain day, comparative exceptions were made to determine the qualities of the salts employed, it would be an error, something similar to Mr. Blanchard’s, for the result would not be a solution of the questions of iodides and bromides, but simply a comparison of the different degrees of sensitiveness &c., of several collodions particularly salted, when in their best serviceable conditions—a matter particularly of importance to those who manufacture collo dion. A sensitive plain collodion, with decided organic re action, is, I think, well adopted for rapid work. By reason of those organic reactions, the decay of the collodion will be rapid; but it is a great help to rapid work to be able to extemporise, at a moment’s notice, as it were, in quantities suitable for temporary requirements, instead of having several pints of cadmium collodion ripening on their shelves, and which may not be available in their best serviceable condition when most needed. With such a collodion a large quantity of bromide is admissible. As intensity accompanies organic reaction, the bromide can be made a regulator of it, although the
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