The photographic news

• Bandzählung: 12.1868
• Erscheinungsdatum: 1868
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186800009
• PURL: http://digital.slub-dresden.de/id1780948042-18680000
• OAI: oai:de:slub-dresden:db:id-1780948042-18680000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

May 29, 1868.] THE PHOTOGRAPHIC NEWS. 257 been made with soap and water, there is always a saline dampness exuding from the skin which will produce mark ings on the paper that by no means improves the beauty of the picture aimed after. 3rd. By every precautionary means take heed that the paper at its back be not defiled. Nothing so forcibly shows up a slovenly workman as display of hideous, yellowish, green ish and mud-coloured stains on the backs of the prints he produces. I would as readily condemn a print stained at its back as one spoiled on account of any unconcealable defect. When cutting up paper I prefer’using scissors, placing the paper before me, sensitive surface upwards. If carte size pieces are needed I cut the paper into two halves, again divide into quarter sheets, and once more subdivide into quarter-size pieces. A sheet of paper thus treated should yield thirty-two carte prints. For pictures of larger dimensions the requisite mode of procedure will be readily suggested to those who make up their minds to go in for perfection. It will be observed that I do not fold the paper at all, and it is surprising how accurate the eye becomes after a brief allowance of practice. Moving on another stage, I ask care and attention in the “ filling in of frames.” Don’t be over “ cheese-paring cut the paper large enough, for it is wise at all times to allow a margin beyond the extremities of the negative for handling purposes. When fingering the paper the fingers should, as much as possible, be applied to its edges ; never must they be permitted to touch the surface on which any portion of the picture is to appear. The remarks contained in the above threefold division deserve the careful attention of those who are desirous of obtaining clear and delicate prints, The reward I offer to all who will digest and practise the hints embodied in those paragraphs are unsullied prints, on surfaces as brilliant as the albumen surfaces they received from their photographic paper dealers. The subject of printing now demands attention, and I ask my reader to recall to memory the sun versus shade printing controversy which, a few months since, engaged the pens of Mr. Cherrill and myself. Since that time I have paid special attention to the subject, and the results of my numberless experiments have more than ever convinced me that sun printing (save under rare exceptions) is altogether a mistake, oft-times the unsuspected cause of failures and un satisfactory results. If the several gradations of a negative that range, without perceptible divisions, from opacity to transparency, maintained a proportional power to resist light under all circumstances, sun printing would, under such conditions, be perfectly admissible ; but on reflection it must bo admitted that such is not the case. Direct sun light finds ready entrance where diffused light would be for a longer time excluded ; hence it follows the weaker light effects a considerable reduction in the deeper shadows ere the higher lights become at all changed. A second and no less forcible protest against sun printing presents itcelf. When an excited albumen surface is exposed to diffused light, the most sensitive salt first succeeding that salt being the chloride of silver, the print for a considerable time is seen to assume a violet hue. If the light is very weak the picture finishes up without reduction, to any extent, of the organic salt; but in ordinary diffused light, with the now usually weak salted paper, the albuminate of silver goes to make up to a considerable extent the last printed half of the picture. Thus we have the softness of the chloride picture with the vigour and persistency which the albuminate of silver- im parts, and together, perfection is to a considerable extent worked out. But alter the conditions ; instead of printing in diffused light do so in the direct solar rays: what is the result? The albuminate of silver is reduced at once; a superficial film of the reduced organic salt is made to form the picture; the dense portions of the negative are pene trated long before the shadows have attained the requisite depth, and you have a poor, flat print, which, in some in stances, appears as mealy before toning as one that had been exposed to the most virulent attack of chlorine. Reason why: If the surface of a negative is closely examined, it will in most instances be perceived that the deposit by re-develop- ment is not perfectly even, that some portions are more transparent than others ; the defect described is not seen when the print is executed in diffused light, but sunlight penetrates direct, everywhere, and registers everything. My advice, therefore, must be, print in diffused light, except you have a specimen of the ancient “ soot-and-whitewash negative to deal with; then by all means print by the direct solar rays. The quicker the printing qualities of a negative, the deeper the gloom in which the printing should be conducted. I frequently allow a whole day for printing a copy from a negative which, in sunlight, would yield hundreds of copies in the same time. But quality makes ample amends for loss of quantity. As I am soon to enter on toning matters, if you make up your minds to try my new-fashioned method, do not print much deeper than needed in the finished pic ture, and place it in your portfolio, where it must remain until my next, which, on account of the many demands I have received, will soon put in an appearance. And until details are given, pray accuse me not of egotism. COLODION-CUIR AND THE CARBON PROCESS. BY M. DESPAQUIS. At the April meeting of the French Photographic Society, the author demonstrated the practical working of the pro cess he employs to obtain photographs in pigments by means of collodion mixed with castor oil, a compound de nominated collodion-cuir. The film of collodion on which the pictures are produced may either be rendered dull and semi-opaque, like ground glass, or may be left in its original transparent condition, the prints in the latter case having the appearance of glass photographs. Throughout the pro cess ordinary spring water may be used, and the gelatine employed, so long as it is soluble, need not be of the finest quality; it is as well sometimes to add a few drops of ammonia to the gelatine solution, to prevent the formation of air-bubbles when the material is being poured upon the glass or paper surface. The best colouring matter that can be used in the process is indian ink of the finest quality which has been carefully filtered ; for portraiture no other pigment is admissible. Lamp-black and other similar materials, although very finely ground, always produce a disagreeable effect in the delicate half-tones of a portrait, where the minute grains or particles of the pigment are visible. For landscape photography, however, lamp-black may be used with advantage ; it is more intense in colour, and likewise more moderate in cost, for- while 100 grammes of it may be obtained for half-a-crown, the same amount of colouring would scarcely be produced by a litre of indian ink, costing from twelve to sixteen shillings. To improve the tone of the prints, various colours may be added to the blacks employed, such as arehil red, Prussian blue, purple, &c.; indigo is also one of the finest colours that may be used, as it is soluble, and produces no grain. Unfortunately, mixtures containing indigo preserve their sensitiveness for a very short time only, and it is necessary, therefore, to employ the same within twenty-four hours of its preparation. In fact, whenever any other pigments but indian ink, or a car bon black of some kind, are employed, the sensitive mixture does not retain its qualities unimpaired for more than a week, fortnight, or at most a month ; whereas compounds made up with indian ink and bichromate of ammonia pre serve their sensitiveness for twelve months or more. If bichromate of potash is added, the mixture soon loses its sensitiveness, and becomes useless after a period of two days. The formula? used are as follows :— Gelatine 10 to 12 grammes Indian ink 20 „ (Or of lamp-black a sufficient quantity.) Water ••• 80 „ Colours according to circumstances.