For several years past sheet steel has been used in large quantities, instead of copperplates, by the engravers. By this fortunate application of so durable, and, it may be added, so economical a material, not only has a new field been discovered admirably suited to yield in perfection the richest and finest graphic productions, which the ingenuity of modern art can accomplish, but to do so through an amazingly numerous series of impressions with-out perceptible deterioration. The art of engraving on iron or steel for purposes of ornament, and even for printing, in certain cases, is by no means a discovery of modern times; but the substitution of the latter material for copper, which has invited the superiority of the British burine to achievements hitherto unattempted by our artists, is entirely a modern practice.
In the year 1810, Dyer, an American mer-chant, residing in London, obtained a patent for certain improvements in the construction and method of using plates and presses, kc., the principles of which were communicated to him by a foreigner residing abroad. This foreigner was Mr. Jacob Perkins, an ingenious artist of New England, and whose name subsequently became so extensively known in this country, in connexion with roller-press printing from hardened steel plates. The plates used by Mr. Perkins were, on the average, about five eights of an inch thick; they were either of steel, so tempered as to admit of the operation of the engraver, or, as was more generally the case, of steel decarbonated, so as to become very pure soft iron, in which case, after they had received the work on the surface, they were casehardened by cementation.
The decarbonating process was performed by enclosing the plate of cast steel, properly shaped, in a cast iron box, or case, filled about the plate to the thickness of about an inch, with oxide of iron or rusty iron filings. In this state the box is luted close, and placed on a regular fire, where it is kept at a red heat during from three to twelve days. Generally about nine days is sufficient to decarbonize a plate five eights of an inch in thickness. When the engraving or etching has been executed, the plate is superficially converted into steel by placing it in a box as before, and surrounding it on all sides by a powder made of equal parts of burned bones, and the cinders of burned animal matter, such as old shoes or leather. In this state the box, with its contents, closely luted, must be exposed to a blood red heat for three hours; after which it is taken out of the fire, and plunged perpendicularly edgewise into cold water, which has been previously boiled, to throw off the air. By this means the plate becomes hardened, without the danger of warping or cracking. It is then tempered, or let down, by brightening the under surface of the plate with a bit of stone; after which it is heated by being placed upon a piece of hot iron, or melted lead, until the rubbed portions acquire a pale straw color. For this purpose, however, the patentee expressed himself in favor of a bath of oil heated to the temperature of 460 degrees, or thereabouts, of Fahrenheit’s scale. The plate being cooled in water, and polished on the surface, was ready for use.
A more material peculiarity in Mr. Perkins’s invention, and one which does not seem to have been approached by any preceding artist, was the contrivance of what are called indenting cylinders. These are rollers of two or three inches in diameter, and made of steel, decarbonized by the process be-fore described, so as to be very soft. In this state they are made to roll backward and forward under a powerful pressure, over the surface of one of the hardened plates, until all the figures, letters, or indentations are communicated with exquisite precision, in sharp relief upon the cylinder, which being carefully hardened and tempered becomes, by this means, fitted to communicate an impression to other plates, by an operation similar to that by which it was originally figured. It will be obvious, that one advantage gained by this method must be the entire saving of the labor and expense of recutting, in every case on different plates, ornaments, borders, emblematical designs, &c., as these can now be impressed with little trouble on any number of plates, or in any part thereof, by the application of the cylinder. At first sight, the performance of such an operation as the one now alluded to, may appear difficult, if not impracticable and, indeed, many persons, on its first announcement, were disposed to doubt or deny its possibility altogether. With a proper and powerful apparatus, however, this method of transferring engravings from plates to cylinders, and rice versa, is every day performed with facility and success, not only in the production of Irish bank-notes, labels, &c., but in works exhibiting very elaborate engravings.Lardner’s Cyclopedia.
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