The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
• OAI: oai:de:slub-dresden:db:id-1780948042-18620000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite 1-72 fehlen in der Vorlage. Vorlagebedingter Textverlust.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

Feb. 28, 1862.] THE PHOTOGRAPHIC NEWS. 107 the photographed block as upon blocks prepared in the ordinary manner. Designs upon metal plates arc obtained by these gentle men by a different process to that usually employed. It is, well known that certain salts of iron, as the lactate, perchlo ride, &c. are modified under the influence of light, and become extremely hygrometric : this is the starting point of the new process. Upon a plate of metal carefully cleansed, they spread a film of gum arabic, which is allowed to drain and dry ; -when dry, it is impregnated by means of a soft brush with a solu tion of tartaric acid and of perchloride of iron, and again left to dry during four and twenty hours. It is then exposed in the pressure frame under a positive or a negative, and, after exposure, the length of which will depend upon the inten sity of the light, the plate is carried into the dark room. The light has decomposed the perchloride into protochloride, and the design appears as a negative; it is next sub mitted for a few seconds to the steam of water, which im pregnates, in proportion to the degree of solarization, the sensitized portions; with a soft brush charged with resin the whole plate is carefully gone over, the resin adheres to those portions which have absorbed steam in greater or lesser quantity. Then, without washing, the plate is heated; the resin melts and forms a grain, which varies according to its thick ness, and thus gives all the tones of black and white correctly. It is afterwards submitted to the usual processes of engraving. Among the new publications of interest to photographers, we may mention M. Arthur Chevalier’s “ Treatise on Enlarg ing Photographs, in a Theoretical and Practical Point of View,” and Messrs. Barreswill and Davanne’s “Dictionary of Industrial Chemistry.” The editor of La Lumiere, M. Gaudin, has some remarks in the last number of his journal upon Emerson J. Reynolds’s printing process with the salts of iron, and on Mr. Hanna ford’s criticisms upon the same. He says:—“Mr. Hannaford's remarks are indeed rather severe, and may be better under stood when it is remembered that he has himself proposed a printing process with salts of iron. He is perfectly correct when he states that the development of images by nitrate of silver must form chloride of silver in the paper, which a simple washing in water would remove, and which might subsequently alter the lights of a proof. Mr. Reynolds, on the other hand, says, that these chlorides must be removed by the ammonia in excess, which exists in the ammoniacal nitrate of silver. This salt has, in fact, always an alkaline reaction to test paper, and it really contains free ammonia: this latter, capable of easily dissolving chloride of silver, also decomposes the oxalate of iron, and produces free oxide of iron, which immediately stains the paper yellow. Does ammoniacal nitrate of silver worthy of the name, that is, prepared with ammonia in excess, and then boiled, dissolve chloride of silver ? This case appears to me doubtful ; I cannot at present throw any light on the matter; but without reckoning, like Mr. Reynolds, upon the free ammonia which may not exist, I rather believe that the solvent power of ammoniacal nitrate of silver will be strong enough to remove naturally the feeble traces of chloride of silver formed spon taneously in the papers of commerce. “ I have continued making experiments to arrive at pro ducing proofs by this process, without having recourse to nitrate of silver; I have ascertained that the peroxalate of iron is more sensitive with a feeble excess of oxalic acid, and especially, when united with organic matter, such as gela- hue; and by this latter addition, I reckoned upon making Proofs which will resist washing, by the gelatine being coagulated; but I was mistaken, a single washing in water caused the image to disappear almost entirely, leaving only a general yellow tint, which, with the tincture of galls, formed a reversed image. The printing always proceeds slowly, and I begin to suspect that this process, which was so seductive at first, presents no superiority over other iron printing processes already published.” Aotograghir Zlotes and Queries. TRANSFERRING Engbavinos to Glass. DEAR Mb. Editor.—In the days when I was young, trans ferring engravings on wood and glass was a fashionable amuse ment, but like poona tinting, and many others of this class, have, I believe, long since ceased to be in request. I remember that the thing to be desired was, that only the ink impression should remain on the glass when finished, and none of the paper. To succeed well, requires a very careful and somewhat tedious manipulation. Procure a tenacious, but quick drying spirit varnish; the engraving must be well soaked for some hours in warm water to take out the size, then dry between sheets of blotting-paper until surface dry only, that the varnish may adhere to the fatty substance of the ink, and not sink into the paper; the glass must be evenly coated with varnish quickly, and perfectly free from dust and bubbles. These operations must be performed in a warm room, the glass and engraving being at such a temperature as not to chill the varnish; the engraving must be quickly and firmly pressed down to the glass in every part, and if any bubbles of air should be between the engraving and glass, prick them with a needle. The varnish must be allowed to dry thoroughly, then the glass and engraving should bo immersed in acidulated water, as you name, for some time ; then, while damp, proceed to rub off the paper by light circular rubs with the finger, dipping the finger now and then into water; when only the im pression remains let it dry, then finally varnish with a pene trating varnish. I have more than once, in out-of-the-way nooks and corners, seen old mezzo-tint engravings transferred to glass, and so finely back-painted as to appear at first sight as old oil paint ings by good masters. I shall be gratified if the above is of service to your corres pondent, Mr. Clarke. T. P. E. The Alkaline Dry Process. Sir,—There is so wide a difference betwixt Mr. Bartholo mew’s mode of preparing his alkaline dry plates, and that sug gested by “ E. T.” in your last impression, that I shall esteem it a favour if you will insert this letter for the purpose of pro moting further discussion thereon, Mr. B. does not anticipate any bad results from a combina tion of the soda and gelatine, because he says that the alkali may be dissolved in it, whilst “ E. T.” states that if any com bination takes place between the soda and gelatine, certain markings “ fatal to good negatives ” will result. Will Mr. B., as the author of this new alkaline process, favour us with his opinion upon "E. T’s.” observations.-—I am, sir, your obedient servant, F. M. Young. London, February 25, 1862. Eliscelluneons. CEMENTS FOR PORCELAIN, MARBLE, ALABASTER, GLASS, &c. Take of isinglass two drachms, wet it with water, and allow it to stand until softened then add as much proof spirit as will rather more than cover it, and dissolve with a moderate heat. Take of gum mastic one drachm, dissolve it in two or three drachms of rectified spirit. Mix the two solutions and stir in one drachm of gum ammoniacum in a fine powder, and rubbed down with a little water. Keep the cement in a bottle. When required for use place the bottle in warm water, and apply the cement with a stick or small hard brush to the china previously warmed. Compress the pieces firmly together until cold, taking care to make the contact perfect, and using a very thin layer of cement. The white of eggs thickened with powdered quicklime is also used as a cement for broken china, marble, and glass. White resin and white beeswax melted and mixed with plas ter of Paris make a good cement for mending alabaster and marble ornaments. A transparent cement for glass is made by dissolving one part of india rubber in chloroform, and adding sixteen parts, by measure, of gum mastic in powder. Digest for two days, and frequently shake the vessel in which these substances are contained. The cement is applied with a fine camel’s-hair brush. The silicate of soda is about the best cement that can be used for mending broken crystal.—Scientific American.