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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
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- urn:nbn:de:bsz:14-db-id1780948042-188300004
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- http://digital.slub-dresden.de/id1780948042-18830000
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- oai:de:slub-dresden:db:id-1780948042-18830000
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- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1297, July 13, 1883
- Digitalisat
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Zeitschrift
The photographic news
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- Titelblatt Titelblatt I
- Register Index III
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446 THE PHOTOGRAPHIC NEWS. [July 13, 1883. that a drop of the etching solution left on a piece of polished zinc for a few seconds should make a slight but visible stain of a light grey colour. If the stain be deeper, add water ; and if lighter, add phosphoric acid. The solu tion being made of the proper strength for ordinary use, can, as required, be weakened or strengthened in the same way. The etching liquid is brushed all over the plate with a broad brush, and allowed to remain for a few seconds, after which it is washed off with sponge and water. The plate is then sprinkled with turpentine (sometimes a little glycerine or oil is added) and a few drops of water, and gently rubbed with a piece of felt kept for the purpose, till the transfer ink is removed. The work must now be rolled in again with printer’s ink, made by thinning down one pound of ink, as sold in tins, with about five ounces of middle and five ounces of thin lithographic varnish, and mixing it well up on a stone slab with a muller. The stiffness will depend on temperature. If too stiff, more varnish may be added, or vice-versa. The ink for proving should, however, be rather stiffer than would be used for printing, especially if the work is fine. Before commenc ing to roll up the plate, the printer should have his damp ing cloth wetted, and wrung out as dry as possible, and having in a basin at his side his damping solution, made by adding two dessert spoonfuls of gum-water to a pint of water. This solution should be kept solely for damp ing the plate, and should be used for no other purpose. All being ready for rolling up, the plate is damped, and the roller is passed over it in the manner to be described in the next section, till the work appears in all its details, and evenly charged with ink all over. Dirty spots or marks and other defects will now appear. The heaviest of these are removed by rubbing them with the pointed end of a piece of wood shaped like a pencil, and dipped into a solution of caustic potash 1 ounce to 4 ounces of water. The printer should take a wet sponge in the left hand, and the stick in the other ; a very small quantity of potash should be taken up on the stick, and rubbed over the dirty mark, then removed quickly with the wet sponge. When all the heaviest marks have been removed, sprinkle a little gum-water over the plate, pass the damping cloth over it, and roll up once more. Now take a piece of felt about six inches square, made into a roll; dip this into a mixture of gum and acid composed of— Nitric acid ... ... ... ... 1 ounce Water 6 ounces Gum-water 2 ,, and rub the acid gently over the dirty places, using the sponge with the left hand as before, until all the dirt is removed. Small spots are removed with the point of a slate pencil or snake-stone slip, and lines that are too thick, or shadows that are too deep, may be treated with the scraper or dry point in the same way as described for stone. When the work appears quite clean, the plate is etched again, sprinkled with a little gum-water, damped, rolled up, and a few proof impressions pulled on thin paper till the plate is clean and in good working order. After proving, the plate should be rolled up, and a sponge con taining gum-water passed all over the surface, and then fanned dry. The plate should always be gummed and fanned dry if left or put away for a time, as dampness will corrode the metal and spoil the work. It should not be put away with too much gum on it, as the gum attracts moisture from the atmosphere. Mr. Richmond recommends a rather different procedure to the above, which may be worth noting. For etching he uses a simple decoction of nut-galls without any acid. The decoction is made by steeping four ounces of bruised galls in three quarts of water for twenty-four hours, and then boiling up and straining. After etching, wash off, gum in, and dry by heat; then wash off the transfer ink with turpentine without remov ¬ ing or moistening the gum, and roll in the plate till quite black. Now sprinkle it with water, and continue rolling and throwing on water till the plate becomes clean again, and the work is properly charged with ink. This method is considered safer, in the first instance, than washing out in the ordinary way. If the work rolls up weak, it may frequently be strengthened by rubbing up with thin ink, which may con tain a little olive oil and plenty of gum. Corrections.— When the proof is examined, it will usually be found that more or less alteration will be required before the work can be printed off; and this is much more the case with photo-lithographic reproductions than with ordinary lithographic work, which always require special drawings, whereas the originals for photography are generally in manuscript, often valuable, and impossible to alter. In map work, for instance, names and details may require alteration, entire removal, or new insertions. The addition of title, foot-notes, border lines, &c , is also sometimes left to be done after proving. In all classes of subjects, more or less touching up and correction is usually necessary, and though it by no means improves the work, should not, if carefully done, injure it very much. As a rule, all cleaning up and slight touching up should be done before proving, leaving actual corrections and alterations to be done after proving, when the work is better pro tected by gum. Corrections on Stone.—Corrections before proving are generally made by scraping the ink off the part with a sharp steel scraper, taking care not to make a hollow in the stone, which would prevent the part printing up. For larger corrections the work may be removed, and the stone polished again with snake-stone, pointed slips of which, or slate pencils, are very useful for this purpose. After polishing, any new details required can be inserted with writing ink or by transfer. Corrections after rolling-in are made in the same way if work has to be removed, otherwise it will be sufficient to remove the gummy coating of the stone by washing it over with a solution of acetic or citric acid, just sufficiently weak not to effervesce on the stone. It is allowed to remain for about a minute, and then well washed off. The stone is then ready for touching up, or additions to be made with writing ink or by transfer. Richmond recommends the stone to be first inked up before the application of the acid, and the superfluous ink to be removed afterwards by pulling an impression or two on plate paper. Usually, however, the ink is first removed, and then the acid applied. In this case the acid used must be weaker, so as not to penetrate the thin coating of ink on the lines. Corrections on Zinc.—For a long time one of the great impediments to the adoption of zinc printing was the sup posed difficulty of correcting errors or making additions after the subject had once been put down and etched. Long experience of zinc printing of subjects requiring a great deal of correction has shown that there is no more difficulty in making corrections on zinc than there is on stone, if due care be exercised. At the same time, they should be avoided as far as possible. Corrections before proving are generally made immedi ately after transfer and before the plate is etched. Faint and broken lines are strengthened with lithographic writ ing ink and a fine brush or pen. Titles, footnotes, and other lettering, &c., may be added from copper plate or type transfers. Parts where the lines run together may be opened out with an etching point. Spots, finger marks, and other imperfections are removed with the wooden point and caustic potash, or with slate pencil or snake stone, as before described. In working on the unetched plate, great care must be taken not to rub the work or touch the surface of the plate with the fingers. When corrections are made after proving, the part of the plate to be corrected must first be washed free of gum, and
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