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. 1393, May 15, 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)
308 THE PHOTOGRAPHIC NEWS. LMAY 15, 1885. The supply-tubes and draw-off may be ordinary gas-pipes fifed through corks into the respective openings left for them. The supply tube is either connected with the main by an india-rubber tube, or is furnished with a funnel, into which water runs from a tap. In the latter case, however, the funnel should be kept out of strong light, or the supply-pipe leading from it should have one or two turns to prevent light from being reflected from the in ternal surfaces of the water into the emulsion. A piece of rubber tube snapped on to the supply inside the lid will serve the same purpose. If there is a room which can be absolutely darkened, where is a supply of water, the basin and sieve may be placed under a tap through which water is allowed to dribble. There should be sufficient force of water to keep the shreds of emulsion in a tremulous motion, when a washing of two hours will generally be found sufficient. If theie is no supply of running water, the emulsion must be frequently stirred, and the water occasionally changed, and in this case it is well to give longer time, say after a few changes, to leave the emulsion standing in water all night. Another plan that has been recommended for more effectually removing the salts is to pass the emulsion a second time through the canvas after it has been washing for some little time, and then to continue the washing. In this case it is well to have the mesh of the canvas large. There are two objections to too fine a division of the emul sion: it is liable to fill up the interstices of the sieve, and so prevent the ready flowing away of the water ; and it retains more of the washing water between the shreds, so that the resulting emulsion is apt to be sloppy. In place of the canvas or netting through which to force the emulsion, some recommend a sort of syringe, the end of which is covered with wire netting, and through this the plunger forces the emulsion. In addition, however, to the objection that this is a special appliance not easily pro cured, there is another : that with this plan the shreds of emulsion are very liable to agglomerate into a mass imme diately after passing through the wires. Perhaps this might be overcome by making the end of the plunger and of the wire cap, cup-shaped instead of flat, as it is to be supposed that this tendency to agglomeration arises from the shreds being driven out in parallel directions instead of divergent ones, so that a very slight expansion is suffi cient to bring them into contact. The emulsion should be set so firmly for squeezing as is consistent with getting it easily through the canvas ; and the water with which it is squeezed should be cold—say not above 60° ; in very hot weather, therefore, it is desirable to put a lump of ice into the water in which the squeezing takes place ; after the first washing the temperature is not so important, but it should never be high enough to render the emulsion slimy. When the emulsion is washed, the water is poured off, and the emulsion left some time on the sieve to drain. It is well to leave it for some hours to get rid of as much water as possible. The importance of having a firmly- setting emulsion is very great, and in the experience of the writer many formulae contain too little gelatine in the finished emulsion to give a satisfactory result. This will be referred to later on, but in the meantime it may be mentioned that in hot weather, or if the emulsion is inclined to be sloppy, it may, after draining an hour or so, have a few sheets of gelatine cut into strips stirred into the shreds of washed and drained emulsion, and after standing long enough to absorb moisture and become quite soft, the whole is melted up together. When the emulsion is sufficiently drained it is collected with the help of a wooden or silver spoon, and placed in a vessel to melt. A jug is very convenient for the purpose. The jug is placed in hot water, and it is desirable not to make the emulsion hotter than is necessary for thoroughly melting it. The outer water may, however, be very hot without unduly raising the temperature of the emulsion, provided that the latter is kept stirred ; and for this purpose a strip of glass, or a wooden or silver spoon, may be used. When melted, alcohol is added (methylated spirit will do) in the proportion of from five to ten per cent, of the emulsion. The emulsion must be well stirred while the spirit is being poured in, to prevent the formation of clots. In order to prevent frilling, it is desirable generally to add a certain quantity of chrome alum to the emulsion. This is stirred in last of all, and with the same precaution referred to in the case of the alcoholic addition. The use of chrome alum has been asserted by some to cause slow ness of the emulsion ; the writer has not found this to be the case. He has commonly used for half a pint of emul sion containing 240 grains of gelatine, half a drachm of a solution of 200 grains of chrome alum to an ounce of water. Some gelatines will take much more than others without becoming thick or ropy ; but it is generally desirable, when the emulsion is not to be coated at once, to defer the addition of chrome alum until it is melted for coating: otherwise the emulsion may require great heat to re-melt it. Lastly, before coating, the emulsion is to be filtered. This is generally performed by pouring it through fine muslin ; what is known as mull muslin is very close, and allows no large particles to pass. A circular piece of this material may have a piece of elastic sewn into a hem round the edge, and this hem stretched over the edge of a glass or porcelain funnel which is of such a size that the muslin hngs as a bag in it without quite reaching the neck. The question of various formul for washed emulsion will be treated later on ; but a simple and good emulsion for a slow one may be made nearly as the unwashed emul sion given on page 202. Gelatine 240 grains Bromide of potassium 90 ,, Water 4 ounces Nitrate of silver ... ... ... 120 grains Distilled water ... 3 ounces Mix as directed for the unwashed emulsion, and keep hot for from two to twelve hours according to the sensitiveness desired. Note.—In the formula for unwashed emulsions (p. 202) the amount of water should read 2 and not 5 ounces. In cold weather the latter might answer, but the smaller quantity is to be preferred; quicker setting favours absence of crystallization. Zebtews. The Magic Lantern Manual.—(Second edition.) By VV. I. Chadwick. Crown octavo, 154 pages. (^London: Warne and Co.) Now that the optical lantern is so generally used as a means of exhibiting photographs, the instrument possesses even a greater interest to photographers than was the case some years ago, and Mr. Chadwick is to be congratulated on having produced a practical and comprehensive hand book on the lantern and its belongings. Tables of Conjugate Foci, with Explanatory Remarks. By J. R. Gotz. (^London : Blacklock, 75, Farringdon Hoad, E.C.) We have here tables showing at a glance the position of original lens and sensitive plate for reproductions, enlarge ments, or reductions, ranging from equal size to 1-300ch, and for lenses from 3 to 36 inch focus. Analogous tabls have appeared in the former Year-Books, and in the PnoTuGRAPnic NEwS, but owing to the circumstance that photographic lenses are seldom made to the exact focus by which they are known, such tables often mislead.
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)