Suche löschen...
The photographic news
- Bandzählung
- 29.1885
- Erscheinungsdatum
- 1885
- 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-id1780948042-188500006
- PURL
- http://digital.slub-dresden.de/id1780948042-18850000
- OAI-Identifier
- oai:de:slub-dresden:db:id-1780948042-18850000
- Sammlungen
- Fotografie
- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
- Bemerkung
- Seite I-II fehlen in der Vorlage. Paginierfehler: Seite 160 als Seite 144 gezählt.
- Strukturtyp
- Band
- Parlamentsperiode
- -
- Wahlperiode
- -
- Bandzählung
- No. 1395, May 29, 1885
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
- -
- Wahlperiode
- -
-
Zeitschrift
The photographic news
-
Band
Band 29.1885
-
- 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 29.1885
-
- Titel
- The photographic news
- Autor
- Links
- Downloads
- Einzelseite als Bild herunterladen (JPG)
-
Volltext Seite (XML)
340 THE PHOTOGRAPHIC NEWS. [May 29, 1885. the film. This accounted for the abnormal density of the images obtained on the collodio-chloride, also for the polished metallic lustre on the gelatino-chloride plates. 1 was determined to develop a good image on the gelatino- chloride, and so I made a mixture of 1 part saturated solu tion of sodium sulphite, and about 1 part saturated solu tion of sodium bi-sulphite, and diluted the mixture down to four times its original bulk. On exposing a gelatino- chloride plate, and immersing it in this solution, to which I had added pyrogallic acid, not a trace of an image appeared for four or five minutes, when a faint trace was seen. 1 left it in the dish whilst doing some other work in the laboratory, and examined it after about quarter of an hour, when I found a developed picture of splendid inten sity, without fog of any description, and of ruby purple tone—just such a tone, in fact, as has been sought after in connection with the gelatino-chloride paper for printing by development. The solubility of the chloride had been checked by the dilution of the developer, and also by the bi-sulphite, and in consequence a good developer, though slow, had been attained. 1 further treated the capabilities of the developer for over-exposed pictures, and found that the image was always under perfect control; in fact, such a developer would be useful in cases of over-exposure, since it is so slow, and yet so sure. Bromide of silver seems to be almost unattackable by it when in the solid state, and when it has been unacted upon by light. It is, to a certain extent, however, soluble in it, and is thus reduced. It strikes me that this property may be of use in giving intensity to a picture by immersing the unexposed negative in a solu tion of pyrogallic acid and sulphite, the increased density being arrived at by deposition instead of reduction of silver. Again, it may be possible to saturate sulphite of soda with bromide of silver, and to cause that slow reduc tion of the latter in a similar manner whilst in contact with a silver image. This fact—that silver bromide in the solid state is very little, if at al), reduced by the sulphite—led me to make some experiments by immersing the plates, during expo sure, in a solution of sulphite and pyrogallic acid. With collodio-bromide plates the images developed during ex posure, and were ready for fixing immediately after with drawal from the dark-slide. With gelatino-bromide plates a trace of the image was visible, and gradually developed by means of the combined developer after a very short time (say two or three minutes). Similar re sults were obtained with the chloride plates. We thus have once more a developer which can be used during exposure without lengthening the exposure, for sulphite of soda is, besides being a substitute for the alkali, also a powerful bromine absorbent. Now, suppose that sulphite of soda can be mixed with pyrogallic acid without altering the composition of the one or the other; it is evident that any other oxygen absorbent should do equally as well as pyrogallic acid. The substance that at once presented itself to my mind was hydrokinone, and it was attempted to develop various collodio-bromide and gelatino-chloride plates with it and the sulphite ; but, so far, I have not obtained a trace of an image when employing them, whilst the smallest addition of pyrogallic acid to the mixture almost immediately called out an image. If this be confirmed by future ex periment it would appear then that pyrogallic acid and sulphite of soda form a new chemical compound which is capable of effecting development; and there seems to be but little doubt that this compound, when oxidised, is nearly colourless. The want of colour in such a solution would, therefore, be no test as to its state of oxidation. Of course, in the development of gelatine plates, this absence of colour means absence of the well-known stain ; hence the use of the mixture. There is, as chemists well know, probabilities of organic sulphites being formed when SO, is brought in contact with them, and this is probably the case in this instance. Once more I endeavoured to attack the sodium sulphite from the iron developer direction. If ferrous sulphate be added to a solution of sulphite, we have an immediate pre cipitation of an oxide forming a gelatinous mass ; if, how ever, to the ferrous sulphate a small quantity of sodium bi sulphite be added, sufficient to cause the solution to be acid after the sodium sulphite is added, no precipitate of any moment forms, and an image is readily developed on a collodio-bromide plate. This action of the acidified solu tion is in keeping with the known properties of ferrous sulphite. Before fixing, such an image appears fairly dense, and will appear at the back of the plate; but after fixing it is weak, very different from the image pro duced by the ferrous oxalate when the same amount of development is effected. As to the cause of this weakness I am at present unable to give any certain reason; but from experiments made by exposing in the solution itself it almost appears as if the image was not metallic silver, but a subsalt, which on fixing is partially dissolved, and metallic silver left behind. This I am investigating, howa ever, together with the behaviour of certain other silver compounds. It seems, then, that sulphite of soda, when combined with pyrogallic acid or with ferrous sulphate, is a develop ing agent, and that with the former it forms a compound which, when oxidized, is nearly colourless. It next struck me that sulphite might be advantageously used instead of hyposulphite in the fixing of prints, and this I tried with marked success. Now, when hyposul phite of soda is in contact with chloride of silver, a hypo sulphite of silver is formed; but I am inclined to think, from some preliminary analysis, that sulphite of soda dis solves chloride of silver without change, as also does sodium chloride. If so, we have no unstable sulphur compound formed, which is an advantage. That the whole of the silver compound which is capable of change in light is got rid of by the sulphite is shown from the fact that a print treated with it does not change in the least in bright sunlight after very long exposure. As to permanency, of course it is too soon to speak ; suffice it to say that it promises well. One word as to its use with gelatine. In one or two instances I have found that the film becomes softened when a saturated solution was employed in the developer— not that there is any tendency to frill, but it becomes tender to the touch. Such tendency disappeared in my plates when they were immersed in the fixing bath. I would call to mind the hydrosulphite developer intro duced by Mr. Sammann, and advocated by Mr. Berkeley. In this, sulphite of soda was needed for the purpose of acting on zinc to obtain the hydrosulphite. EFFECTS OF INTENSIFICATION AND REDUC TION. BY CHAPMAN JONES. There can be no doubt that if an exposed plate is simply developed into a good negative, that negative will be technically of finer quality than if it had required after treatment. But it is well known that a plate may be beautiful from the negative maker’s point of view, and yet be far behind an inferior negative in producing a good print. As the sole use of the negative is to furnish the print, it is not only legitimate, but proper, to treat it in any way that shall improve its powers in this direction; and although the cliche is in the end such a one that we may feel ashamed for any one to see it, we may be proud of the resulting improvements in the picture. Disregarding altogether the use of tissue paper and all retouching operations which are often necessary if we would produce what is true and beautiful, intensification and reduction, either separately or combined, local or general, afford a means of getting results which the writer does not think can be obtained in any other way. “ Intensi-
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)