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The photographic news
- Bandzählung
- 35.1891
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- 1891
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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. 1714, July 10, 1891
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The photographic news
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Band 35.1891
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is a great chance that some of the insoluble silver salts pro duced will be thrown down in the granular form. A is then added slowly to B with much stirring. The emulsion is filtered through a double thickness of cambric, and is then immediately ready for use. If it is wished to keep the emulsion for any length of time, 10 per cent, of alcohol, in each ounce of which a few grains of thymol have been dissolved, should be added to the emulsion. It is to be observed, however, that, even with this addition, emulsion by formula No. 3 will not keep for very long. The best way of coating is certainly by floating, allowing three or four minutes, but the quantity of emulsion needed is considerable. It is possible to get an even coating by brushing with cotton-wool in the following way. The paper is laid on a sheet of glass, or a clean board, and is thoroughly and evenly damped with the solution by brush ing over the surface several times in directions at right angles. It is put on one side for ten minutes or a quarter of an hour to get surface-dry, when the operation is repeated. By working in this way, it is possible to do with a very small quantity of solution emulsion, and it is possible to use what there is to the last drop, but the quantity used will be found to be more per sheet than in the case of floating. The reason, I imagine, is, that it is impossible to get an absolutely even coating by brushing, and that it is, therefore, necessary to make the coating so thick that there will be sufficient silver where it is at its thinnest. I have never been able to get an even enough coating by brushing only once. The temperature of the operating-room should be not below about 70° Fahr., or else the emulsion should be warmed. The paper is best dried pretty quickly before a fire, or near a stove, after it has lain face upwards for about four or five minutes to get partly surface-dry. In fact, the paper is best treated, in the matter of drying, like paper that has been coated with the solutions for the “ hot bath ” platinotype process. It will be found that it is possible to coat about eight sheets of “medium ” sized paper (22 by 17, the orthodox photographic size) with the quantity of emulsion given above by brushing, or ten to twelve sheets with a con sumption of the like quantity by floating. It will thus be seen that the process is an economical one. The colour in the printing frames should be a rich brown with either of the first two formulae, a deep purple with the third. The printing is very quick, whichever of the formulae be used, but with No. 3 it is extraordinarily so. Indeed, paper coated with emulsion prepared by this formula is, I think, more sensitive than that by any other printing-out process that I know of. It is so sensitive that it is quite necessary to take extra precautions in working it. It needs at least all the care that platinotype paper needs, although there is, of course, the difference that, in the case of the silver paper, the result of the action of feeble light is seen at once ; in the case of the platinotype paper it is not seen till the time of development. I consider it best to do everything in the way of preparation by gas or lamplight. Toning may be either by gold or platinum. I prefer Clark’s platinum process to any other. I add, however, a good dose of salt to the solution, and put the prints into it dry ; that is, at least, when using either of the first two formulae. When using the third, the prints are washed in a weak solution of citric acid before they go to the toning bath to neutralise the alkalinity. If a platinotype toning bath that has been used for some time, and that has been repeatedly strengthened with chloro-platinite of potassium, be used, a colour is got that some people dignify with the appellation “ sepia tint,” but I incline to call it a dirty brown. I find that the emulsion is readily applicable to wood, and I hope to get good results when I have had some panels made of one or other of the beautiful white woods, with a fibre-like silk, that are peculiar to this country. I have got very fine colours of image by printing lightly and intensifying, as suggested some time ago by Clark, but have not as yet been able to overcome a tendency to staining in the whites. Perhaps Mr. Clark will help me with a hint or two in connection with this matter. I send a few samples of prints done by the process, but I do not think they are fair examples of what it is capable of. They are all merely some of the results of my experi ments, and are on Whatman’s drawing-paper, which is not very suitable for photographic purposes unless it is speci ally sized, and I have not sized it. It is the only pure matt-surface paper at present procurable in this country. The prints on it look tolerable only from some little dis tance. I hope to have some more creditable results ready later on. There are some words of explanation in pencil on the back of each print.—Paper read at the Camera Club. RETOUCHING AND SPOTTING PHOTOGRAPHS. After printing and toning, photographs are often found to have white spots, and the mediums employed to cover them are often removed in the enamelling and burnishing processes. Mr. Beacham, of Litchfield Street, Soho, W.C., has patented a crayon for spotting and retouching, which is made as follows: White wax, 32 parts; curd, yellow, or Castile soap, 27 parts; mutton suet, 4 parts; salts of nitre, 1 part, dissolved in eight times its weight of water; pitch, 4 parts; shellac, 6 parts ; calcined lamp- black, 4 parts; dyes or stains in powder—brown 74 parts, scarlet 3} parts, blue 3 parts, violet 3} parts. These colours produce a useful photo-shade, but the proportions can be varied according to the shade required; other colours can also be produced if required. As soap con tains more or less moisture, according to age, it must be cut into small pieces and dried before using. The suet and wax are first melted; the soap, having previously been cut into small pieces, is then added a small piece at a time, allowing each piece to dissolve before another is added. When dissolved, they are allowed to burn until reduced to the same volume as before the soap was added. Care must be taken not to allow them to burn too much or too quickly (it may be necessary to take the vessel olf the fire to prevent the contents from boiling over). The flame is then put out. When these three ingredients are dissolved, and the salts of nitre has been mixed with eight times its weight of water and warmed, it is added by small quantities to prevent too much effervescence. The shellac and pitch are added. The requisite colours, in powder dyes or stains and calcined lampblack, are mixed with a stiff varnish or suchlike suitable substance. It is essential for the whole to be dissolved into one substance, and kept stirring during the whole of the foregoing pro cess with an iron spatula or palette knife. When a little I cool, it is poured out on a marble slab previously rubbed
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