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The photographic news
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- 35.1891
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- Bandzählung
- No. 1703, April 24, 1891
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Apbil 24, 1891.] THE PHOTOGRAPHIC NEWS. 319 THE PERMANENCY OF PHOTOGRAPHS* BY FR. WILDE. It has been claimed for platinum prints that they are absolutely permanent. That reduced chloride of silver should not be equally permanent as chloride of platinum still remains to be proven. It is true that hyposulphite of soda does not come into play in fixing the platinotype, and all danger from that source is precluded. I have seen many clear and beautiful platinum prints, but also many which had turned very yellow. Platinum paper is notoriously unstable, and must be used fresh; if this is not done the result is doubtful, and the prints usually useless. Perhaps the poor specimens seen were the result of stale paper, or, possibly, the cause was that traces of muriatic acid remained in the paper. Last May I saw an exhibition of platinotypes, of universal excellence and clearness of tone, in a prominent photographic establish ment. Several months later I again saw them in the same position. All had not kept equally well; a few had dis coloured a little, but the majority were unmistakably yellow. Consequently, it is also requisite to exercise caution in the manipulation as well as in the selection of materials for platinotypes, if the prints are to remain without change. Such being the case, the much-vaunted platinum process has, as a matter of fact, no advantage over the silver print. Notwithstanding the beauty of the platinotype, which is acknowledged by photographers in general, the process is used by comparatively few. The cause for this may be that platinum paper is an expensive material, and the process requires much practice before the requisite experience is obtained which alone insures success. The failures are expensive, and cause much loss of time ; and furthermore, specially prepared negatives are requisite to produce good results. Now it is suggested to tone silver prints with platinum, and thus obtain prints with all the characteristics of platinotypes. Here the silver is replaced with platinum ; accepted that it is true that platinum chloride gives more permanent prints than silver chloride, then by this method the substitution of platinum for silver would be easy and cheap; further, it does not bring into play a single pro cess with which every photographer is not familiar. The process differs only in the substitution of a platinum for the gold bath. A platinum bath yields more and keeps longer than a gold bath. As a fact, the process gives excellent results, and is worthy of the attention of all photographers. In our own practice, we use a plain paper. Platinum toning has been frequently broached, but the experiments usually resulted in measly prints if tried with albumen paper, or flat, grey prints on plain salted paper. The cause for these failures was that the baths for sensi tisingpaper for platinum toning should contain ammoniated argentic nitrate. I never was in favour of such baths, asthey do not keep, and are useless for albumenised paper. Still,itis convenient to have a bath which will answer for all papers. I made the trial with paper, sensitised on my regular bath for albumen (1’8) three minutes; then I fumed on both sides four to five minutes shortly before use. The result exceeded the expectation ; quick printing, plucky, beautiful tones, brilliant high lights, with the richest scale of half-tones down to the deepest shadows. The paper used was a strong, heavy Steinbach, with a rough surface, notwithstanding which all the finest detail and modula tions were present, which added greatly to the artistic * Concluded from page 265. effect. Before toning, the prints must be well washed until the water does not show the least trace of milkiness. They are then well drained, and placed in the platinum chloride bath. They tone rapidly, after which they are placed in a strong bath of common salt; and from this into the fixing bath (hypo 1-6), in which they remain twenty-five to thirty minutes. After the fixing, I proceed as with silver prints. I place them in the salt baths until, according to the chewing test, there is no by-taste. These saline baths act well, and strengthen the tone of platinum as well as silver prints. Another matter which has a tendency to improve the prints is a rapid drying after a thorough washing. In mounting, a rapid drying by gentle heat also tends to act advantageously. It is remarkable how indifferent the majority of photo graphers on the Continent are to the fuming of sensitised paper, in view of the great advantages to be gained with so little trouble and loss of time. Fumed papers are much more sensitive, and copy in less time than the plain. The prints are as strong with the use of a weak silver bath 1-12 to 1'16, as the unfumed sensitised on a concentrated bath ITO to 1-8. The prints on the former have a finer detail and shades in the half-tones, and details often lost come out here in all their beauty. Ready-sensitised paper only gives good results if fumed with ammonia. The prints then are equal to freshly sensitised paper. This paper is of great advantage to smaller photographic estab lishments, as it is possible to prepare a quantity of paper in advance. This saves time and trouble. The following formula has proved the most reliable in my experience; it seems to be of special trustworthiness, and deserves the attention of the practical photographer. The paper is floated for two or three minutes on a solution of— Nitrate of silver ... 100 grams Citric acid ... ... ... ... 100 ,, Water ... ... ... ... 1,200 c.c. Alcohol 100 „ After each sheet has been sensitised, 10 c.c. of the follow ing solution are added to the bath :— Nitrate of silver ... ... ... ... 20 grams Citric acid 12 , Water ... ... ... ••• ••• 200 c.C. Alcohol ... ... ... ... ••• 20 » When removed from the bath, the paper is drawn over a glass rod, and, after draining, placed with the sensitised surface on chemically pure blotting-paper. It is then covered on its back with a sheet of stout paper, and well and evenly wiped off by powerful rubbing and pressing. Finally it is dried spontaneously in the dark. If placed between preserving paper, it will keep for from six to eight weeks in summer, and for months in winter. The pre serving paper consists of soft, very thick, unsized blotting- paper of white colour, which should be entirely free from wood, chemically pure, and saturated with carbonate of soda. It should be used in rolls of from five to six metres length, and kept, together with the sensitised paper, in pasteboard or tin boxes. At a recent meeting of the Royal Meteorological Society, it was noted by Mr. F. J. Brodie, as one of the features of the past winter, that the number of foggy days in London was no less than twice the average. The California Camera Club, says Anthony's Bulletin, gave a very interesting lantern exhibition during the last of March, on which occasion the views were entirely of picturesque English scenery, embracing many of the noted castles and ruins of the old country, and it was much enjoyed by all pre sent.
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