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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
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- Englisch
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- F 135
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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. 274, December 4, 1863
- Digitalisat
- SLUB Dresden
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Zeitschrift
The photographic news
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Band
Band 7.1863
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- Register Index 619
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Band
Band 7.1863
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December 4, 1863.] THE PHOTOGRAPHIC NEWS. 581 in all written instructions; to those we would say, feel assured there is no concealment. Failures are produced by a non-observance of some indispensable conditions, to produce those tones so temptingly described in the pages of the PIOTroqRAPIIO News, it is absolutely necessary the prints be produced from a really good negative, clear in the shadows and perfect in all its details. The paper employed should not be too highly salted, and we are convinced that under all circumstances, the richest tones will be secured by an adop tion of the nitrate of soda bath for sensitizing chiefly on account of the bright red colour it produces when the paper is exposed to light. When associated with lime, the gold precipitated on a dead surface assumes a hue anything but agreeable to an educated eye; but with a warmly tinted foundation, the deposit acts as a subduing glaze through which the colour beneath penetrates, imparting that richness that forms the chief characteristic of properly managed limo toning. In attempting to produce black tones with the old alka line solutions (so called), an unpleasing inkiness generally presents itself, though with less exposure to their action, a colour is imparted to the prints, which, before fixing, appears everything that can be wished for, but one moment’s con tact with the hypo, and the promising hue is vanished for ever, simply because this fugitive colour is imparted by chlorine in its secondary formed union with silver reduced by the action of light, a substance that is soluble in the fix ing solution. The combination last alluded to has given birth to an error that is entertained even among high authorities, because a certain portion of silver is displaced from the paper’s surface, during ordinary toning operations it is considered that such a result must necessarily ensue in order that the gold may take up its abode on the ground rendered tenantless by the ejected silver, and that toning action can only proceed under those conditions. To prove the fallacy of this mode of reasoning, it is only necessary to give our method of toning a trial when it will be found that with the absence of free chlorine, bleaching influence is removed, and in spite of a liberal allowance of acid roaming at large in the solution, tones can be secured that will pass unscathed through the ordeal to which they are subjected during the process of fixing, MM. Davanne and Girard notwithstanding. To secure the above described results, we proceed to construct our toning solution as follows :—A stock bottle containing 8 grains carbonate of soda to the ounce of water, is laid aside in a convenient corner; on the same spot lies another bottle, in which is placed a saturated solu tion of chloride and carbonate of lime, allowing the excess of both substances to remain precipitated in the bottles; when ready for toning operations, we add to each grain of gold 10 minims of the soda solution, and on this mixture is poured a small quantity of boiling water to drive chlorine in a direction where it is unable to practise its mischievous tricks. So soon as the yellowness disappears, the mixture is thrown into the toning dish, and the necessary quantity of solution is made up with pure water, allowing about a quart to the grain of gold, from two to three drops to the last named quantity of the lime is then filtered into the dish, and we are ready for work. The solution may be used con tinually instead of fresh water each time, and during cold weather double the portion of gold above named may be added with advantage. It is best to tone all the batch of prints at one time : like Parkinson’s formula, it moves slowly, and therefore cannot injure by causing untonod spots, if the prints arc kept turned. A bath thus prepared is decidedly acid, although from the quantity of water used, the particles are so widely separated by dilution, their presence remains undetected by ordinary tests; but if its acidity is doubled, it is only necessary to test the solution in a more concentrated form ; indeed, without a liberal allowance of acid, the bath refuses to work, and from this fact wc arc able to judge the necessary quantity of the alkaline agent to be applied, and non-toning when the proper allowance of gold is present, usually means too much soda. Printing must be carried no further than required in the finished picture, as it strengthens rather than bleaches in the solution we have described; and in toning the same conditions must be observed, as the colour imparted does not change in the fixing bath. Before fixing, the prints should be first passed through a water containing a small quantity of carbonate of soda, another liberal allowance of washing, and fix in the usual manner. The part played by lime in toning would be difficult to decide. One thing is certain, where that substance is employed, if the excess of chlorine is first driven off by heat, the small quantity remaining makes no attack on the silver, as it does in the absence of lime, and the same results follow when an ordinarily prepared lime bath has got rid of its chlorine by long keeping. From these facts we are inclined to believe that the small quantity of chlorine liberated is absorbed by the lime ere it reaches the surface of the paper, hence the colour is imparted by the gold alone, which substance protects the print from further reduction when exposed to the fixing action. And now, in conclusion, we would just observe that no royal road to photography exists. In offering formulas or directions, we do not promise invariable success to anyone, but to all who will master the principles we have done our best to lay down. We promise the ability to overcome diffi culties which may present themselves. In our experience we find in printing operations materials for continual study. Every day brings to light some new difficulty, whose charac ter can only be detected by close observation, and whose dangerous tendencies can be conquered only by means that are based on scientific principles. In concluding our first series of “ Jottings,” we would just observe that, from motives of fair play, we have refrained from recommending the materials supplied by any dealer; but should the cause of failures arise from defective paper, we are willing to supply the name of our favourite maker, by directing, under cover to us, to the office of the PHOro- GRAPMI News, with a stamped envelope Jor a reply. ON TONING PAPER POSITIVES. BY C. OMMEGANCK. Aithough the auro-cupric bath we lately recommended has given results superior to those obtained by every other pre paration, we shall, notwithstanding, give some indications respecting two other very useful formulae, because a great many photographers, having acquired a certain experience of these two formulae, determine not to abandon them. The two formulae in question are, 1st, that of acetate of soda, and, 2nd, that of hypochlorite of lime. Gold Bath with Acetate of Soda. Water 1 litre 354 fl. ozs. Acetate of soda 20 to 30 grammes 309 to 464 grains. Chloride of gold ... 1 gramme ... 15,8 grains. The acetate mentioned above is the crystallized acetate (C 4 H 6 O 3 , N a 0 4- 6 HO) =139 : it contains, as may be seen, six equivalents of water: we can employ with advan tage the anhydrous acetate of soda (twice fused), first in its water of crystallization, and afterwards submitted to an igneous fusion); it has the same formula as the preceding, minus the six equivalents of water (6 H 0) : the sum of the constituent equivalents, or its total equivalent, is 85. Between these two salts the relation is therefore as 139 is to 85, or, in round numbers, as 3 is to 2; therefore 30 grammes of crystallized are equivalent to 20 of fused anhydrous. Commercial crystallized acetate of soda is slightly alka line ; the fused acetate is ordinarily very strongly so. The preparation is made by dissolving in the water first the acetate and then the chloride of gold. Decoloration takes place slowly, and the bath is not fit for use until the morrow, and sometimes even four or five days after the pre-
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