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The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1294, June 22, 1883
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Zeitschrift
The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
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Band
Band 27.1883
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- Titel
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JUNE 22, 1883. ] THE PHOTOGRAPHIC NEWS. silvering. As the bath will take up but very little of the alum, a few drachms will remain in saturation some length of time, and not until this is taken up is renewal necessary. This bath is self-renovating, needs no tonics to settle its stomach, and never fails to respond to your call. Don’t all try it at once, and bring on a corner in alum. PHOTO-LITHOGRAPHY AND PHOTO ZINCOGRAPHY. BY MAJOR J. WATERHOUSE, B.S.C., Assistant Surveyor-General of India. Chapter X.—Principles of Lithography, and Materials Required.—continued. The proper consistence of the ink is a most important point, and one that requires considerable experience to properly master. The softer and thinner the ink is, the more readily it will leave the roller and deposit itself on the lines, and the greater the tendency will be for the work to clog up and be too heavy by the spreading of the lines when passing through the press, and also by the too great absorption of fatty matter. Very thin ink may form a scum all over the stone or plate, and as such will not have sufficient tenacity to clean up the work as the printing proceeds ; each impression will add to the mischief, so that in a short time the stone or plate will be irretrievably ruined, yielding only dirty, smudgy, unpresentable prints. On the other hand, if the ink is too stiff, it leaves the roller with difficulty, and the rolling-in becomes tedious and fatiguing. The ink also, having more attraction for the roller than for the stone, will not be deposited in proper quantity on the finer and more delicate parts of the work, and they will be gradually worn out. Further, stiff ink, requiring along and heavy rolling, is aptto stand in relief on heavy lines, and smash in taking the impression. It may also stick so strongly to the surface of the paper as to tear it on removal. Very fine close work, such as the reproduction of a fine engraving, where it is of importance to keep the lines sharp and the spaces between them open, will require a stiffer and better ink than open line work. For proving, rather a stiffer ink should be used than for printing. A good ink should contain as much colour as possible, com bined with just sufficient varnish to make it easily work able, so that it may yield a sufficiently dark impression without lying too thickly on the lines, possessing at the same time sufficient tenacity to clean well off the stone when the roller is used smartly, without risk of impoverish ing the finer parts, or sticking to and tearing the paper. It must also be borne in mind that temperature will greatly affect the consistency of printing-ink and varnish, the thin gaining in stiffness in winter, and the strong losing it in summer. Krom the above remarks, it will be apparent that success in lithographic printing is mainly dependent upon the rollers being in proper condition, and skilfully used with ink of suitable consistence and quality. Coloured inks may be bought ready ground and mixed ; but they are generally made up as required by first taking some middle varnish, and working as much powder colour into it as possible with the palette knife. The mixture is then ground with a muller, and being gathered up again with the palette knife, more colour is added, and the mix ture is ground again, these operations being repeated till the ink is so stiff that the face of the muller will no longer pass over it, and the edge must be used. The lighter the tint, the more varnish is used; and in some cases flake—or better, zinc white—are added to give body while reducing tint. carbolic acid may be added, and the mixture stirred occasionally till all the gum is dissolved, forming a solution about the thickness of syrup ; it is strained through a cloth, and will then be fit for use. Gum-water has a strong tendency, especially in summer, to become sour and acid, in which state it should not be used, because it acquires too strong an “ etching ” property. The addition of a little chalk, or lime-water, will keep it neutral; or some antiseptic, such as carbolic acid, camphor, or thymol, may be used with very good effect io preventing it from turning sour. As noticed before, the principal object of the gum is to prevent the spreading of the ink forming the lines of the drawing. It should, as a rule, be applied when the stone is dry ; it then penetrates and holds better in the pores of the stone or metal, forming a close and insoluble combi nation which cannot be washed away by repeated moisten ing of the surface. It thus surrounds the lines of the drawings, and, by its complete impermeability to greasy matter, preserves their purity by preventing them from spreading. When stones or plates are put away after printing, or even during any short interruption of the printing ‘he stone should be washed over with gum. The co ing should, however, not be too thick, or it will be lia e in warm, dry weather to scale off, and may bring away por tions of the stone with it. It is sometimes recommended to rub the stone over gently with the hand, until the gummy coating is dry. Gum-arabic is often adulterated with cheaper gums, principally gum Senegal, which, however, having much the same properties and perfect solubility in water, is equally effective; but cherry and other similar common gums, being insoluble, are useless for lithography. Gummed stones or plates must be kept in a dry place, though not too warm. If kept in a damp place, mould is liable to form, causing spots which will spoil the work. The addition to the gum of a little carbolic acid or other antiseptic, as before noticed, helps to prevent this. (To be continued.) Uorrespondence. MULTIPLEX CAMERA BACK. Sir,—In your last number of the Photographic News, you give a notice and illustration of a multiplex camera back, by Messrs. Hare and Dale, Ludgate Hill, which I think in some respects requires explanation. In the first place, I was not aware there was such a firm as Messrs. Hare and Dale. I think it should be H. and E. J. Dale, with which firm I have no connection whatever. 1 should not have noticed this, had not several of my friends and customers supposed I am the Hare referred to. Such is not the case, however, as I am still trading as I have done the past twenty-seven years as George Hare. Further in your notice you say, “ An adaptation of the principle of the revolving album is not altogether a novelty ; indeed, we believe an apparatus of this kind was first constructed as a container of dry plates.” In this you are quite correct: an appaiatus of this kind was cinstructed, and the revolving album was an offshoot from it, but it was not designed by the Messrs. Dale, and it is not so certain and simple in its action as is stated ; it is not quite easy to bring a plate in position, particularly if plates of differing rapidity are used in tbe same box.—I am, sir, yours respectfully, Georgs: Hare. [The designation “ Hare and Dale ” was taken from a printed circular.—Ed. P.N.] Gum.—This substance takes such an important place in lithographic operations that a few remarks are necessary regarding it. It is used in the form of a solution in water, made by putting a quantity of good gum-arabic, at about a Is. or Is. 61. a pound, into a suitable vessel, and covering it with water. A few drops of THE BRUSSELS EXHIBITION. Dear Sir, We beg to draw the attention of your readers to the following :—For apparatus, lenses, photographic
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