Volltext Seite (XML)
RECIPE IV, Solution A. Water ... ... ... ... 1,000 c.m. 3 Sodium sulphite ,.. 35 grammes Ferrocyanide of potassium ... 25 3 Hydroquinone ... ... (1.) Natrium hydric, depur. Mix per cabinet plate— 10 3 A ... 60 c.m. 3 B (caustic soda 1 • 2) or ... 6-9 c.m. 3 A ... 60 c.m. 3 B 1 (caustic soda 1 • 3) ... 10-12 c. m. 3 The image does not appear for about five seconds, and is fully developed in one to two minutes. The gradation is very good ; the plate remains clear in the developer, and portraits, even though taken on dull, misty days, pro duce excellent results. As compared with the pyro-soda plates, they were excellent. All these developers are convenient to handle. In the morning one may mix a sufficient quantity for the whole day, or for several days. As far as my experience goes, the mixture keeps well in closed bottles, and I could not notice any decomposition after eight days. If, how ever, one wished to produce the mixture in equal quan tities immediately before use, it would be easy to calculate it out, e.g., Recipe IV. into Recipe V.— Solution A. Water ... ... ... ... ... 550 cm. 3 Sodium sulphite 35 grammes Ferrocyanide of potassium 25 33 Hydroquinone... 10 33 Solution B. Water ... ... 550 cm. 3 Caustic potash... ... 50 grammes or— Solution B', Water ... ... 550 cm. 3 Sodium hydrate ... 60 grammes Mix per cabinet plate— A (Recipe V.) ... 30 cm. 3 B or B' ... 30 cm. 3 When travelling, it is advisable to keep a supply of the developer concentrated. Uecipe for a Concentrated Rapid Hydroquinone Developer.— A. Dissolve 25 to 30 grammes of sodium sulphite in 100 c.m. 3 of water and 10 grammes of hydroquinone warm; then 25 grammes of ferrocyanide of potassium likewise in 100 c.m. 3 of water. The two solutions are mixed, and produce 200 c.m. 3 B.—Dissolve 50 grammes caustic potash in 100 c.m. 3 of water, or 30 grammes of caustic soda in 90 c.m. 3 of water. For a cabinet plate mix— A Water ... B (caustic soda 1 :2) ... or— A Water ... ... Caustic soda +3 ... ... 10 cm. 3 ... 40 cm. 3 ...6 to 8 cm. 3 ... 10 cm. 3 ... 40 cm. 3 ... 10 cm. If one mixes the 200 c.m. 3 of solution A with 100 c.m. 3 of B, one obtains a mixed concentrated rapid developer, which must be thinned for use—10 c.m. 3 to every 30 c.m. 3 of water for rapid developments. Thus, the concentrated solution of 300 c.m. 3 sufficesfor 1,200 c.m 3 of the finished developer, but which may again be diluted with 1,000 c.m. 3 of water for slower developments, and with 10 grammes of hydroquinone one gets more than two litres of ordinary developer. Solutions A could also be used in conjunction with potash or soda, and then one has ordinary, but very good, potash or soda developer, e.g. :— Soda Developer. A (Recipe IV.) ... ... ... ... 30 cm. 3 Solution of soda (1-r 5) ... ... ... 30 cm. 3 Rapidly acting developer may be made also with potash hydroquinone, of which another time. The potash deve loper requires a developing of about five minutes, the soda developer of four to five minutes. All developers with sodium hydrate and caustic potash hydrokinone may be diluted with an equal volume of water ; the development is restrained thereby, but the details do not suffer. Bromide of Potassium (1 • 10).—Ten drops to the quantity mentioned have a powerfully restraining effect, by which chiefly the details of the shadows suffer. It is quite different with iodine and iodide of potassium, the effect of which I have fully described. Antichlor acts restrain- ingly on the hydroquinone developer, but it is not to be recommended for that purpose. The developed plates must be well rinsed, and fixed in an acid fixing bath. One must take care that the fixing bath produces an acid reaction, which may easily be achieved by an occasional slight addition of an acid solu tion of sulphite.* The fixing bath should be frequently renewed, because an accumulation of solution of sulphite would finally restrain the fixing. For fixing with the acid fixing bath, cuvettes are much to be preferred to trays. The fixing will proceed much quicker, particularly if the plate-carrier is moved up and down with the plate several times. Now that with these developers the developing pro ceeds with a rapidity which hardly leaves anything to be desired, it would be well to artificially accelerate the fixing, which might certainly be accomplished by means of indifferent additions to the emulsion. If one develops a large number of plates with the rapid developer, it is desirable to have at hand a vessel of water containing a few drops of sulphuric acid. When the fingers become slippery, one dips them into this acidified water, by which means the feeling is immediately removed. The developing trays after use should be rinsed first with the weakly acidified water, and then with spring water. PHOTOGRAPHY and Painting. I must add a postscript to my last letter. In Germany, and formerly in Austria, photographs were considered as mere manufactured articles, but later, in Germany, somewhat better protection was afforded them by a new law. Nevertheless, copyright for life, or for a certain number of heirs, was by no means granted for them. In Austria, repeated judgments of the Supreme Court of Justice decided that photography is to be reckoned among the fine arts, and to be protected against unauthorised reproduction ; but, for a long time, painters looked down on it, and would not recognise its co-ordination. The International Photographic Exhibition, planned by the Club of Amateur Photographers in Vienna, will be the first occasion on which a jury meets clearly recog nising the co-ordination of photography, and, at the same time, containing men like Professor * 1,000 cm. 3 of water, 300 g. of sodium sulphite, 70 cm. 3 of concentrated hydrochloric acid, or mercantile acid solution of sulphite.