The photographic news

• Bandzählung: 35.1891
• Erscheinungsdatum: 1891
• 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-id1780948042-189100009
• PURL: http://digital.slub-dresden.de/id1780948042-18910000
• OAI: oai:de:slub-dresden:db:id-1780948042-18910000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

July 24, 1891.] THE PHOTOGRAPHIC NEWS. 531 The process is applicable both to paper and to textile fabrics. The paper or fabric is coated with a solution of a diazo-sulphonic compound of high molecular weight, mixed with an equivalent quantity of a pheno), or a naphthol and an alkali, or with an equivalent quantity of | an amine and an acid. The patent specification recom mends sodium ditolyltetrazo-sulphonate, but Feer has since recommended sodium diazopseudocumidine-sulphonate, which can be obtained from Dr. Schuchardt, of Gorlitz. My own experiments, which are as yet but few in number, were made with this compound and B-naphthol. An ex posure of ten seconds to comparatively weak sunlight pro duces a very decided quantity of colouring matter, and an exposure of a very few minutes gives a deep-coloured print. The rate of formation of the colouring matter decreases as the exposure continues, because the colouring matter formed in the superficial layer acts as a screen to the unaltered material behind. The light from burning magnesium will also produce a print, and prolonged expo sure to gaslight will produce an easily recognisable amount of colouring matter. Some “ nature prints ” from fern leaves are exhibited ; they show a very considerable amount of detail as well as the outline. The primuline process is the second process of this class, and is the invention of Messrs. Green, Cross, and Bevan (English Patent 7,453, May 13th, 1890). Primuline was first made by Mr. Green, and is a yellow colouring matter that contains sulphur. It has the peculiar property of dyeing cotton, linen, paper, or any other material consisting of cellulose, without the use of a mordant. The exact constitution of primuline is not yet known, but it contains an amido group, and, therefore, will yield a diazo com pound, which in its turn will form colouring matters. Diazo-primuline in the pure, solid state, is practically un affected by even prolonged exposure to light, but when in contact with cotton, linen, or cellulose it is rapidly decom posed by light, with complete destruction of the diazo compound and consequent loss of the power to form colouring matters. The primuline process is applicable to fabrics as well as to paper, and gives better results with the former. Herein, in fact, lies its special merit. Fine calico, linen, &c., free from grease, is immersed for a short time in a boiling solution of primuline (about 3 parts in 1,000) containing a small quantity of common salt, and is then washed with water. If necessary, it may at this stage be dried, and will keep for any length of time. In order to sensitise the material, the primuline is converted into diazo-primuline by immersion for a short time in a dilute solution of sodium or potassium nitrite (1 part in 400), acidified with hydrochloric, sulphuric, oxalic, or some other acid. It is then washed and dried in the dark without the aid of heat. If made too dry the material becomes less sensitive. The sensitive material is exposed in an ordinary printing frame, a very short time being required in bright sunlight, but a much longer time in a dull light. Since the correct time of exposure cannot be judged by mere inspection, a strip of the same material is exposed outside the printing frame, and is touched from time to time with a drop of the developing solution. When the latter ceases to produce any colour, the diazo-primuline on the test strip is com pletely decomposed, and it may be taken that decomposition in the high-lights of the transparency is also complete. The print is then ready for development, which is effected by immersing the print in one of the following solutions :— For yellow, phenol; for oranye, resorcinol; for red, B-naph- thol; for maroon, B-naphthol-disulphonic acid. One part of the substance is dissolved in 4C0 parts of water, made alkaline with caustic potash or caustic soda. Other deve lopers are: for brown, meta-phenylenediamine ; ior purple, alpha-naphthylamine ; for deep blue, eikonogen. The eikonogen is dissolved simply in water; the two amines are dissolved in water acidified with hydrochloric acid. Different developers—stiffened, if necessary, with starch may be applied with a brush to different parts of the same prints. The developed prints are washed with water, and, in the case of the blue and purple developers, the last wash water should be slightly acidified with tartaric acid. In the other cases the prints are improved by being washed with soap and water. In all cases the appearance of the print is improved if, after removal from the printing frame, the back of the print is exposed to light for a short time in order to secure complete decomposition of the diazo- primuline in the high-lights. The ground of the prints always remains pale yellow, and, at present, no method has been discovered by which a white ground can be obtained. In Feer-type the quantity of colouring matter formed is proportional to the quantity of light action, and hence we obtain a positive from a negative, and vice versd. In the primuline process the quantity of colouring matter is inversely proportional to the amount of light action, and hence we get a positive from a positive, and a negative from a negative. The prints, being formed of azo-colouring matters, will J gradually fade if exposed to sunlight, but are permanent enough if exposed only to the diffused light of ordinary rooms. Neither of the diazotype processes is at all likely to displace any of the ordinary printing processes, but they may be specially useful for the copying of engineers’ plans, &c., upon cloth, and, since a variety of colours can be obtained, the processes are likely to be very useful for decorative purposes. The primuline process is very simple and cleanly, and can be readily used by ladies, who, with the help of dried ferns and other leaves, can produce a great variety of designs on linen, &c., and these can be mounted in any desired manner. In this connection, it may be useful to point out that the disagreeable smell of the purple developer (alphanapbthylamine), which clings very tenaciously to the fingers, can be removed by dipping the fingers into the solution of nitrous acid used for sensi tising the primuline. WHAT WASTES TO SAVE, AND HOW TO SAVE THEM. What would the family photographer say to his wife if he knew that one-half of every barrel of flour he pro vided for his household was allowed to fall under foot, or to be burned in the stove as fuel? And yet we dare to say that one-half the photographers allow at least one- half of the precious metals they purchase for picture making to be wasted as wickedly as though its cost was no greater than that of common flour. One pound of silvered albumenised paper in good health—i.e., when it is clean and free from nails and bits of tintype plates, cardboard, glass, or other dirt and solids—is worth from forty to fifty cents, according to the strength of the silver । solution, the amount of salting in the paper, and the treat ment of it. This value is somewhat reduced by the exposure of the sensitised paper to the light, for a part of the silver is thus rendered insoluble, and so recovery of all the silver is beyond the power of chemistry. Yet, after all, nearly sixty per cent, of the silver you purchase