Suche löschen...
The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
- Lizenz-/Rechtehinweis
- Public Domain Mark 1.0
- URN
- urn:nbn:de:bsz:14-db-id1780948042-188300004
- PURL
- http://digital.slub-dresden.de/id1780948042-18830000
- OAI-Identifier
- oai:de:slub-dresden:db:id-1780948042-18830000
- Sammlungen
- Fotografie
- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
- Strukturtyp
- Band
- Parlamentsperiode
- -
- Wahlperiode
- -
- Bandzählung
- No. 1304, August 31, 1883
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
- -
- Wahlperiode
- -
-
Zeitschrift
The photographic news
-
Band
Band 27.1883
-
- Titelblatt Titelblatt I
- Register Index III
- Ausgabe Ausgabe 1
- Ausgabe Ausgabe 17
- Ausgabe Ausgabe 33
- Ausgabe Ausgabe 49
- Ausgabe Ausgabe 65
- Ausgabe Ausgabe 81
- Ausgabe Ausgabe 97
- Ausgabe Ausgabe 113
- Ausgabe Ausgabe 129
- Ausgabe Ausgabe 145
- Ausgabe Ausgabe 161
- Ausgabe Ausgabe 177
- Ausgabe Ausgabe 193
- Ausgabe Ausgabe 209
- Ausgabe Ausgabe 225
- Ausgabe Ausgabe 241
- Ausgabe Ausgabe 257
- Ausgabe Ausgabe 273
- Ausgabe Ausgabe 289
- Ausgabe Ausgabe 305
- Ausgabe Ausgabe 321
- Ausgabe Ausgabe 337
- Ausgabe Ausgabe 353
- Ausgabe Ausgabe 369
- Ausgabe Ausgabe 385
- Ausgabe Ausgabe 401
- Ausgabe Ausgabe 417
- Ausgabe Ausgabe 433
- Ausgabe Ausgabe 449
- Ausgabe Ausgabe 465
- Ausgabe Ausgabe 481
- Ausgabe Ausgabe 497
- Ausgabe Ausgabe 513
- Ausgabe Ausgabe 529
- Ausgabe Ausgabe 545
- Ausgabe Ausgabe 561
- Ausgabe Ausgabe 577
- Ausgabe Ausgabe 593
- Ausgabe Ausgabe 609
- Ausgabe Ausgabe 625
- Ausgabe Ausgabe 641
- Ausgabe Ausgabe 657
- Ausgabe Ausgabe 673
- Ausgabe Ausgabe 689
- Ausgabe Ausgabe 705
- Ausgabe Ausgabe 721
- Ausgabe Ausgabe 737
- Ausgabe Ausgabe 753
- Ausgabe Ausgabe 769
- Ausgabe Ausgabe 785
- Ausgabe Ausgabe 801
- Ausgabe Ausgabe 817
-
Band
Band 27.1883
-
- Titel
- The photographic news
- Autor
- Links
- Downloads
- Einzelseite als Bild herunterladen (JPG)
-
Volltext Seite (XML)
546 THE PHOTOGRAPHIC NEWS. [August 31, 1883. at the same time place the third piece in a fresh mixture of alum and hypo. It will be found that that piece which was put into the hypo, direct fixes first; that which was first soaked in alum comes next; but the piece placed in the mixed solutions takes much longer than the other two. Wash all three pieces, and place against black cloth or paper. The second piece may be more or less milky in appearance, according to the amount of washing it received after it had been in the alum, but the third is undoubtedly turbid. This turbidity is not so noticeable on drying, nor need we lay much stress upon it, even if the cause of it were the precipitation of sulphur in the film, as the sulphur would not do the same mischief to a negative that it does to a silver print. The main point to which we desire to draw attention is the difference in the length of time—a difference which, as we shall presently show, can be very readily explained. As we pointed out, this precipitate may be filtered off, but this operation entails a great deal of trouble, and the filter paper used must be of the very best; in fact, this experiment is a very good test for the quality of a filter paper. We would recommend our readers to try this for once by way of experiment ; but filtering a solution to free it from sulphur in daily practice may be objected to; and we purposely avoid, if we can, all chemical reactions in which sulphur is precipitated. We will assume, therefore, that our readers, after passing the mixed solutions through filter papers innumerable, have at last succeeded in getting a clear filtrate. You lay it aside, but only to find soon after that it is again getting turbid. But this is not likely to be very apparent unless the weather is warm. The following experiments will give some idea of what takes place. Into a test-tube pour portions of the solutions of alum and hypo, and heat over a Bunsen or spirit lamp; it is of no consequence which re-agent is in excess. The warmer the liquid gets, the more turbid it becomes, until, by the time it has reached boiling point, there is a large quantity of precipitate, and a suffocating gas—sulphurous acid— is coming off in appreciable volume. This reaction between hyposulphite of soda and salts of alumina is well known to chemists, and is usually expressed by the follow ing formula, leaving out sulphate of potash or ammonia (the other constituent of alum) as not being essential. 3Na,S.0, + Al:(SO.)3 —Al.0, + Sa + 3S0, + 3Na,SO, "VPB."te Alumina. Sulphur. Bullate What takes place in the cold, therefore, is exactly the same reaction, only it takes place much more slowly. We have, then, pretty direct evidence, that when solu tions of alum and hyposulphite of soda are brought into contact, mutual decomposition takes place. To say the least of it, therefore, we are to some extent weakening the xe-agents at our disposal. We run the danger of introducing alumina and sulphur into our films, and sulphurous acid into the atmosphere. But this is not all. By the mere action of mixing the two solutions we weaken both, for each is diluted in proportion to the quantity of the other that has been added to it. This will in itself account for the greater length of time the plate takes to] fix. Looking at the subject from all points, there fore, little or nothing is really gained by mixing the re agents, or time being saved, less economy found, and objectionable substances being brought into play ; whether any trouble is really saved we must leave our readers to judge. On this point we may give the method the benefit of the doubt; but even then we have still to answer the question—Is the game worth the shot? MOUNTING PRINTS. UNTIL improvements in photo-mechanical printing methods enable us to economically and conveniently im press the photographic image directly upon cardboard, the work of mounting prints will form a considerable item in the labour account of the photographer ; as the public look with but little favour upon an unmounted picture, the number sold is comparatively small. A mounted photograph is seldom so flat and even as the original card, because the albumenised paper, expanded by the moisture of the adhesive material used, contracts in drying, and distorts the card mount ; this distortion being generally so considerable, that in the case of a print mounted upon a large card, a decided concavity of the picture results, while a small card nearly covered by the photograph is generally drawn either into a gutter or a bow-like form. These disadvantages can be readily overcome by adopt ing the simple and easy expedient of gumming the prints, allowing them to dry, and then causing them to adhere to slightly damped mounts by the application of considerable pressure. The work of gumming the back of the photographs can be very quickly performed if a broad brush is used, but as the gumming of paper is now a distinct trade in London, it is more advantageous to send them to be gummed, more especially when the sheets are printed upon whole. A ream of paper, the same size as the ordinary sheets used for photographic purposes (17} by 214), can be gummed in London for about 10s., this sum including the gum. The gummed pictures are next trimmed in the usual way, when all is ready for the work of mounting. A card is very slightly damped on the face with a sponge, the gummed photograph is placed in position, and the whole is quickly run through a lithographic or a roller press. Far less moisture is required than might be sup posed, as the pressure brings to the surface that water which has soaked into the card, and the mounted photo graph, when taken from the press, is, to all appearance, as dry as if it had not been damped at all; and, what is more important, it has no tendency to curl. A smooth lithographic stone forms the best basis upon which to lay the print when the pressure is applied, and a sheet of smooth card or glaze-board should be laid over the picture before the leather tympan is closed down upon it. Assuming the pictures to be already gummed, about four hundred per hour can be mounted by this method, and it must be remembered that the effect of the pressure is almost equivalent to rolling. The method to which we now refer has long been in use by collotype printers, in this country and abroad, for mounting their pictures, and we know of several instances in which it has been introduced with advantage in portrait studios. A small lithographic or autographic press, suit able for work up to about 12 by 10, can be obtained for a very moderate sum. THE TOURIST PHOTOGRAPHER. In the Engadine—II. One of the most charming features of the Engadine is the chain of lakelets that occupy the basin of the upper valley. These are not to be seen from Pontresina, but still they are only a two hours’ walk from that village. These waters are of singular beauty. They are placid, green-bordered lakes, the water so clear and translucent that the shining pebbles of red and yellow at the margin seem like bright mosaic work ; at first sight they resemble the ornamental waters of a park, so lawn-like is the green grass, and so dainty and elegant in shape are the clear little basins after the rugged mountain side and monster peaks to which the eye has grown accustomed. The most refined of these pretty waters—a fitting abode for a lady of the lake—is that at Silvaplana, that greets the traveller on his ascent of the steep Maloja pass, when, after an arduous hour or two of climbing, he suddenly reaches the garden-like plain of the Engadine, and gets his first glimpse of the fairy waters. It is very like climbing Jack’s beanstalk and
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)