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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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- SLUB Dresden
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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 7.1863
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- Register Index 619
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582 THE PHOTOGRAPHIC NEWS. paration, according to the state of the atmosphere, the nature of the paper, the neutrality of the nitrate bath, and also the more or less alkaline state of the acetate of soda. This bath usually disengages a very strong odour of acetic acid, and gives an acid reaction with litmus paper; it trans forms into acetate of silver the traces of nitrate still remain ing in the paper at the moment of immersing the proofs: acetate of silver is quickly sulphurized by contact with the hyposulphite. The proofs at the moment of being taken out of the toning bath, have an odour of acetic acid: they really are acid; when immersed in this state in the bath of hyposulphite of soda, they assume a beautiful black tone ; but they are exposed to an energetic sulphurisation, and subject to rapid deterioration. By washing them in abundance of water before fixing, we can, up to a certain point, palliate this evil. A washing in water containing a minimum quantity of carbonate of soda, neutralizes, it is true, the free sulphuric acid, but may cause many other inconveniences, among others that of causing blisters upon removing the albumen from the surface of the paper. The addition of carbonate of soda to the gold bath, prescribed by some, will be the best remedy; but its practical effect, according to our experience, is to render the acetate entirely superfluous. The partial substitution of phosphate of soda for one portion of the acetate of the same base, for example, 15 grammes of the one to 15 grammes of the other, gave very good results; but in our eyes it presents the objection of uselessly complicating the formula;, and of augmenting, without motive, the collection of photographic chemicals. Bath of Gold and Hypochlorite of Lime. Water ... ... 4 litres ... 141 fl. ounces Carbonate of lime ... 10 grammes 154 grains Hypochlorite of lime 1} „ ... 23 „ Chlorite of gold ... 1 „ ... 156 „ Preparation. Put the carbonate and hypochlorite of lime into a mortar, and add sufficient water to form a creamy paste, then add the chloride of gold, and triturate together until an intimate mixture is effected, then leave it to repose for a quarter of an hour to an hour, according to the sur rounding temperature, or as the quality of the paper is more or less subject to a corrosive action in the gold bath; then it is stirred into a litre of water, and the solid por tion is allowed to deposit; it is then filtered, and the other three litres of water are added; this is when it is required for immediate use ; when it is proposed to keep it for some days before using it, the quantity of water is diminished one half, the other proportion remaining the same. If a consi derable time elapses, it may be that the bath will not tone at all; but the addition of 2 or 3 drops of the 10 per cent, solution of chloride of gold will render it active. On removal from the gold bath, the proofs must be washed in two waters, or in one only, if very abundant. This bath is the most economical we know of, as to composition, be it understood, but not always as to use, it requires many pre cautions for the good preservation of the proof, which must be printed very strong, without which the half-tones will be lost. Without washing the proof previous to immersion in the hypo bath, it causes sulphurization, produces sulphide of silver, and a disengagement of sulphurous gas, &c., and proofs that will not remain permanent. It is often complained that toned proofs turn brown in the hyposulphite, without the tone returning after the solution of the salts of silver. Various causes may lead to this much dreaded result. However, they all end in a too superficial toning. The following are the principal circumstances under which they may bo produced. Paper that has been nitrated a very long time—proofs kept a long time before being toned—paper moist at the time of printing—paper become slowly humid by exposure [December 4, 1863. to the atmosphere between printing and toning—silver bath too weak or too strong in nitrate of soda or ammonia, in consequence of long use—paper dried too slowly after contact with the silver bath or left to dry spontaneously in winter. The paper must be dried in less than an hour, and by artificial heat if necessary, interposition of humid paper or flannel behind the positive paper during the printing, and, lastly, and most frequently, a bath too poor in gold, too much reduced by fear of corroding the proofs. It may sometimes happen that we are afflicted with paper of bad quality, from the remnants of dealers’ stock, or bad manufacture. Paper deteriorates with age, and even in a very short time if not kept in a very dry place. In winter, the toning must take place in a very warm room, beside a fire. The operation may be advantageously performed upon a water bath, kept at a temperature of 68° to 77° F. We shall add some advice for those who have found that our formula for the auro-cupric bath has a corrosive action upon the paper they make use of. First, the bath may be prepared several hours in advance. In winter, the prepared bath may be put into a bottle, which is placed in a large jar or other convenient vessel containing water heated to 104° F., and left it in from half an hour to an hour, without, however, applying a source of heat to main tain the temperature at 104%. We shall conclude by some very curious remarks upon the peculiarities encountered in the colouring of the paper. Albumenized paper contracts a different hue, both in printing and in toning, according as the negative has been developed with iron or with pyrogallic acid; and, if deve loped with iron, if it has been intensified to a blue-black by a salt of mercury—if the printing has been performed in the sunshine or in the shade—and if the sun has sensibly warmed the negative or not—if the negative is varnished with white varnish or with brown, when the difference in the colour of the negative is not even evident to the eye— if the glass upon which the negative is taken is blue, yellow, green, or violet—if, being of the same composition, it is thick or thin—lastly, if the sensitive paper exposed to the sun is in repose, or put into rapid rotation. It might, how ever, be supposed that we should mention here the more or less vigorous coloration resulting in a given time, according to the different media through whic.i the light must pass. This difference also exists : it would be useless to dwell upon it, unless we proposed to inquire into the various modes of producing it, and their causes. What we have endeavoured to point out is a difference of tone, the vigour of colour being the same.—Bulletin Beige de la Photographie. DESCRIPTION OF A SELF-ACTING WASHING CRADLE, WITH SOME OBSERVATIONS AND EXPERIMENTS ILLUSTRATIVE OF THE PRO CESS OF WASHING PHOTOGRAPHIC PRINTS. BY CORNELIUS HANBURY, JUN., F.C.S., ETC. Durino the late beautiful summer I was induced to devote a little time to the practice of photography, after having laid it aside for nearly nine years. I found that, during this long interval, some important improvements had been made in various parts of the collo dion process. But, so far as I have learned, no great change has taken place in the general mode of washing prints, although the great practical importance of the operation early attracted attention, and numerous methods have in consequence been suggested for increasing its efficiency or diminishing the labour it entails. The common plan of placing several prints in a vessel, through which a stream of water is allowed to flow, has always appeared to me very insufficient, unless some special and rather troublesome precautions are taken. I was theret fore glad to find that similar views are expressed by Mr Poning in his instructive little work, entitled “ Photographic
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