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Typo: A Monthly Newspaper and Literary Review, Volume 2

A New Auto Stereotype Process

page 27

A New Auto Stereotype Process

How to obtain a fac-simile plate from printed matter is a problem that has long exercised the ingenuity of inventors, and some very elaborate processes have been devised. While any such process is liable to abuse by affording facilities for piracy, it has a wide field of useful and legitimate application. A correspondent of the English mechanic describes an auto-stereotypic process lately invented in Switzerland, and successfully used at the celebrated establishment of Orell, Fussli, & Co., Zurich. It appears to be simple, and requires no costly appliances. It is thus described:—

Plaster of Paris, best quality, is mixed with water to make it a thin putty without lumps, and to this a little alum or salt is added to make it set quickly. To every 51b of the plaster are then added: Silicate of potash or silicate of soda, 3oz., phosphate of lime, 2oz. The mixture thus obtained is then put upon a perfectly level piece of plate glass of the desired size, around which iron rods are placed, and left to get hard. The plaster cast ought to be at least type high, to prevent breakage. While the mass is setting, the back ought to be scraped level, and should remain undisturbed until it is perfectly dry and hard. After that, it may be taken off, and it will be found to be as smooth as the glass itself.

The paper to be reproduced is next placed, with the side to be copied down, in a dish which contains the following transferring solution:—Distilled water, 16oz.; alcohol, 90°, 5oz.; acetic acid, ¼oz.; phosphate of soda, ¼oz. Care should be taken not to get the solution on the back of the paper, which is not to be transferred, as it is then liable to print through when it is drawn through the transferring press. Should the print to be copied have been printed for some time, it is desirable to warm the solution and float the paper longer on it. The sheets should be left on the solution for at least two hours to insure perfect action. In the mean time, the plaster of Paris plate, which was completely dried before, is prepared in a dark room. A solution of 5oz. of gelatine in 12oz. of water is prepared by letting the former soak for half an hour and then heating it to about 190°. Care must be taken to prevent the boiling of the solution. To this, six drachms of citrate of iron and ammonia and 2oz. of alcohol are added and well filtered. This is when still warm. Put into a flat dish covered to a depth of about ¼-inch. It is well to put this dish upon a hot metal plate, as it gets hard quickly when getting cold. The plaster of Paris plate, which itself is warmed first, is dipped in the solution on the smooth side for a moment, thus letting it take up some of it, whereupon it is taken out and dried in the dark. When dry, the copy is transferred upon it in the usual way, the plaster having been placed between rubber sheets to prevent it from breaking. Of course, also, this has to be done in the dark room, that is, at lamp or gas light. The plate is then dried once more and exposed to direct sunlight for 15 minutes. When taken out, the places where the light has acted will be found to be quite hard, while at the other places the plaster is soft, and will fall off as fine powder as deep as the solution has penetrated, if brushed with a hard brush. After that the plate is ready to be stereotyped.