The photographic news

• Bandzählung: 13.1869
• Erscheinungsdatum: 1869
• 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-id1780948042-186900000
• PURL: http://digital.slub-dresden.de/id1780948042-18690000
• OAI: oai:de:slub-dresden:db:id-1780948042-18690000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Heft 545 (S. 73-84), Heft 547 (S. 97-108), Heft 589 (S. 599-610) fehlen in der Vorlage. Paginierfehler: Auf Seite 444 folgt Seite 443
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

10 The photographic news. earthy substances held in suspension in turbid water, it becomes fit to drink in from seven to fifteen minutes if to each litre there be added .01 grammes of finely-powdered alum, care being taken to agitate the liquid when the alum is introduced (this is about 4 lb. per ton of water). It potash alum is used the alum is decomposed into sulphate of potash (which is all dissolved by the water) and sulphate of alumina, which, by its decomposition, purifies the water. The alumina separates in an insoluble torm, and carries down with it, as it precipitates, the matters which render the water troubled, and the organic matter. The acid attacks the alkaline and earthy carbonates and transforms them into sulphates. The water becomes slightly richer in bicarbonates and free carbonic acid, whilst all organic matter is destroyed. Seven parts of sulphate of alumina will purify as much water as ton parts of rock alum or potash alum, and the sulphate of alumina does not introduce any alkaline sulphate into the clarified water.— Technologiste. Gorresponenre. OPERATING EXPERIENCES. Rectifying Old Baths—Iodide or MERCUIY Intensifyer— Paper Discolovrino—Sugar in the Printing Bath. Dear Sir, —On the 27th March this year you were pleased to publish some of my experiences with baths. Four of these were afterwards spoiled by my adding too much permanganate, which made them have the effect of being alkaline. A few drops of nitric acid were added, which helped them for a day, but next day they were as bad as ever. They were treated so for several days. At last one of them got half an ounce of the acid, which was too much for it, as you may well suppose, for it refused to work at all. The four baths were then amalgamated, but as they did not give any promise of doing well, they were laid aside, and ever since have continued to throw down a light deposit; and though they have been carefully filtered several times, they still continue to throw more down. They may do some good yet, but probably reducing them to carbonate of silver will be the wisest thing to do. Other two new ones were got ready and laid by until the three that were still good, and which were being used one after the other, showed signs of exhaustion, when they were taken up, and the old stains on the negative made their appearance again, and refused to leave. At last the new ones were mixed with the old ones, and made into five baths (or one large bath) of 33 grains to the ounce, which were used one after the other as formerly; strengthened when neces sary. They have done duty for six or seven months, and can be taken up at any time with as much certainty as ever. Sometimes needle-like crvstals fell to the bottom of some of them; these were simply filtered out, and the bath was as good as ever. In May last I dissolved 2 ounces of silver in 2 ounces of water in a blue glass bottle, and fastened it to the top of my glass house, and it remained thus exposed to all kinds of weather for about six months, when it was taken down and water added until it indicated 33 grains of silver; was filtered, and it made a good bath at once, without any addition whatever, not showing the least inclination to leave the matt stains on the negative that have vexed one so much for two or three years past when commencing a new bath. There appears to be a change somewhere, but whether on the water, or silver, or the two in combination, the writer of this cannot pretend to say. Being one of those who intensify with iodide of potassium and bichloride of mercury, as described by you in the last part of your article on 9th October—having adopted this method as the most convenient—I have noticed, with “ Amateur ” (Photographic News, December 4th) the ten dency of some plates to turn light yellow, and have blamed imperfect washing, or the solution being used too strong, as the cause. I also notice that one or two negatives taken four or five years ago, and which had been brought up to [January 1, 1869. the yellow tint, are showing signs of fading, while others taken about the same time show no signs of change of any kind. I never wash with anything but clean water. There was a sample of paper fell to my lot this season, that, half an hour after it was sensitized, turned nearly as brown as copper ; one and a half minutes was my usual time for floating on a 70-grain bath for (say) three years. This paper was laid aside until an opportunity was given for experimenting with it, for proof was given by the gentleman* who supplied me with it that it could not only be used, but that it was a first-rate paper. So, after a month or two, I found that twenty seconds’ floating instead of one and a half minutes was what was wanted to make it “all right.” Four cartes are sent along with this, not only as some indication of what may be done with the above baths, and to ask you as under, but also to show you that a darker background has been used by me for “ figures printed out,” and to thank you for the suggestion. The young lady reading was taken with the bath that was made with the silver solution that had been sunned so long before it was made up ; the gentleman was taken with one of those that was mixed new and old together; the other two are sent to see if you will be so good as to inform me if sugar in the printing bath should give me No. 2, which was printed on the day after it was sensitized, as pure in the white as No. 1, which was printed, toned, &c., the same day it was floated for twenty seconds on the bath ; or is No. 2 as pure as may be expected?—1 am, dear sir, yours truly, W. C. [In our experience, paper floated on a printing bath con taining sugar has given prints with perfectly pure whites after keeping some weeks. But there is, doubtless, a differ ence in samples of paper. But all the cards ate good, No. 2 showing very little indication of discoloured paper.—Ed.] COCKLING OF LARGE PRINTS IN PRESSURE FRAME. . « Every little makes a mickle.” Sir,—To what I am going to communicate here, Messrs. So-and-so would say, “ Any fool knew that!” I’d excuse them, for when I made the little fact plain to myself, said I to myself, “What a fool thou must have been not to have seen that before!” Many times have I been vexed, in printing, that some times the albuminized paper would not lie flat in some places, however much packing I added to increase the pressure. At other times the whole paper print is ruffled. My printer often tells me that it is of no use to dry the paper before the fire (when I want things quickly done), because it always cockles-up the paper.” 1 have had serious losses in large prints from this cause, so I turned my atten tion to it the other day. The packing is the cause. Warm the papers or cloths thoroughly before they are placed in the pressure-frame, and no more cockling. The reason is self-evident; and some amateur will thank me for having drawn his attention to it.-—-Yours truly, 0. G. REJLANDER. Ualk in tbe. Studio. AMERIOAN National Photographic Association.—An association of photographers has recently been formed in the United States, aiming to have a national character, and to ex tend its action and influence throughout the whole of the States. We have recently received a courteous letter from its esteemed secretary, to the following effect:—“My dear sir,—At a meeting of ‘ The National Photographic Association,’ held in this city, * Mr. Stuart, of Glasgow and Helensburgh, to whom I am obliged for | many useful hints.