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Typo: A Monthly Newspaper and Literary Review, Volume 3

Inventions and Processes

page 129

Inventions and Processes.

Improvements in Galleys and Locking Arrangements.—The Liberty Machine Works advertise and illustrate a new solid brass rivetted galley which would be « hard to beat, » and a most ingenious galley-lock, dispensing with quoins, sidestick, and shooter. The old quoin and shooter should by this time be obsolete.

Paper-making.—Some novel processes in the manufacture. of paper (says a contemporary) have been suggested, and it is ascertained by experiments in this direction, that the strength of paper is materially increased by the employment of seaweeds, which form with water—certain kinds of them in particular—glutinous liquors; resin soap and aluminous cake or compound may also be advantageously added under certain circumstances. Experiments also show that a very bright surface may be given to paper by the following simple method: A very concentrated cold solution of salt is mixed with dextrine and a thin coating of the fluid laid on the surface of the paper by means of a soft broad brush, and it is then allowed to dry. The most desirable salts for this purpose are sulphite of tin, sulphite of magnesia, and acetate of soda, and sized paper is also essential.

New Process of Reproduction.—The following process permits of easily reproducing on stone or zinc either old or recent impressions. Its chief recommendation is simplicity, for it may be put into practice in any litho establishment. The operation is as follows:—Prepare a clear solution of gelatine, pour a thin layer on a litho stone or on zinc, and allow to dry. Prepare a solution of alum; place therein the verso of the printed sheet to be reproduced, allowing the alum to penetrate the substance of the paper without traversing the printing-ink forming the drawing or the letters of the recto. Place the recto on the stone or on the zinc, and pass to press. By the pressure the alum with which the paper is saturated renders the gelatine insoluble in warm water wherever it touches the unprinted parts of the paper, whilst every part of the gelatine which has only been touched by the ink of the drawing or letters is unaffected by the alum. These parts are therefore soluble in warm water. Remove the paper, which should remain intact, and pour some warm water on the coating of gelatine. This water only dissolves those parts of the gelatine covered by the ink of the paper—that is to say, which were not rendered insoluble by the alum; at other parts, which correspond to the blank of the paper, the insoluble gelatine remains intact. Allow the surface to dry. When it is dry, ink it, and the black will adhere only to those parts uncovered with gelatine, and which now reproduce the letters or drawings in negative. The stone or zinc may now be prepared for working in the ordinary way. The same operation applies to both the recto and the verso of the paper. This method avoids spoiling the original if it does not form part of a book; it permits of reproducing all the delicate parts of the drawing; it is very economical, as, except the ordinary litho material, it demands only a little alum and gelatine.—Inland Printer.

New Sensitive Ink.—A communication has recently been made to the Academy of Sciences by M. Péchard, which those on the outlook for a novelty may turn to account at once. It relates to the peculiar physical properties of oxalomolybdic acid, which is an acid obtained by adding molybdic almost to saturation to a hot solution of oxalic acid. The liquid becomes syrupy, and on evaporation yields crystals of oxalomolybdic acid, C2H2O4MoO3H2O. The acid is almost totally insoluble in strong nitric acid, but dissolves in cold water, more rapidly on warming, yielding a colorless and strongly acid liquid. It forms well-defined salts. The strange thing about the acid is that when the crystals are dry they may be preserved unchanged either in sunshine or in the dark; but if moist they quickly become colored blue when exposed to the sun's rays. If characters be written on the paper with the solution they remain visible in a weak light, but when exposed to sunshine they rapidly become visible, turning to a deep indigo color. This only happens when the solution is spread over paper or other surfaces, for the solution itself may be kept unaltered in the bottle for any length of time, except for a trace of blue at the edge of the meniscus, where, by surface action, a little is spread against the interior glass walls. If a sheet of paper be immersed in a saturated solution of the acid, dried in the dark and then exposed behind an ordinary photographic negative, a very sharp print in blue may be obtained by exposure to sunlight for about ten minutes. The color instantly disappears in contact with water, so that if a piece of this sensitised paper be wholly exposed to sunlight, one may write in white upon the blue ground by using a pen dipped in water. If, however, the paper with its blue markings be exposed to a gentle heat for a few minutes, the blue changes to black, and the characters are then no longer destroyed by water.—Comptes Rendus.