Solinus and Isidore both express themselves in a manner the reverse. But although this may leave us in some doubt, it appears pretty clear that they did not attempt to cut that valuable production with its own dust, or to give it different faces, or render it more brilliant by the same means. If this point was settled, there could be no great difficulty in affirming or negativing the fact of their engraving upon that stone. Thus doubts appear to increase on this head, for Mariette denies that they did; Natter appears uncertain; and Klotz asserts with confidence it was certain. His authority, to be sure, has been considered not to be of much weight.
The proper question, however, appears to be, whether the Greeks and Romans used diamonds for cutting and engraving other stones or glass. Natter, in his work already noticed, thinks they were employed on some antique engravings. His authority is deserving respect. But if they were employed on other stones, the authority which at present directs us, confidently alleges they did not employ them in cutting glass; but he points out the mode in which that article was wont to be divided, in the following terms: “They used for that purpose emery, sharp-pointed instruments of the hardest steel, and a red-hot iron, by which they directed the rents at their pleasure.”
The first mention which appears to occur of the use of the diamond for this purpose, is recorded of Francis I. of France, who, fond of the arts, sciences, and new inventions, wrote a couple of lines with a diamond, on a pane of glass in the Castle of Chambord, to let Anne de Pisseleu, Duchess of Estampes, know that he was jealous.
About 1652, festoons and other ornaments, cut with a diamond, were made on Venetian glasses; then considered the best. Schwanhard was a professed adept in that art; and since his time an artist of the name of John Rost, of Augsburg, cut some drinking glasses, which were purchased by the Emperor Charles VI., at an extravagant price.
ETCHING ON GLASS.
An acid to dissolve siliceous earth was discovered as late as 1771, by the celebrated chemist Scheele, in sparry fluor. It is conceived that this cannot be of older date than that period; but it is alleged that an acid was discovered as early as the year 1670, by Henry Schwanhard. It being said that some aquafortis had dropped, by accident upon his spectacles, the glass being corroded by it, he thence learned to improve the liquid that he could etch figures and write upon glass. How he prepared this liquid is a secret which has not been revealed. The Teutsche Akedemie says on this subject, that he, by the acuteness of his genius, proved that which had been considered impossible could be accomplished; and found out a corrosive so powerful that the hardest crystal glass, which had hitherto withstood the force of the strongest spirits, was obliged to yield to it, as well as metals and stones. By these means he delineated and etched, on glass, figures of men, in various situations, animals and plants, in a manner perfectly natural, and brought them to the highest perfection.
The glass proposed to be etched is made perfectly clean and free from grease; then the figure is covered with a varnish; then an edge of wax being raised round the glass, the acid is poured in, and the whole ground on the exterior of the figures appears rough, whilst the figure is preserved in its original beauty of outline, bright and smooth. This is the mode the inventor adopted.
Professor Beckmann says, he mentioned this ancient method of etching upon glass, to an artist of the name of Klindworth, who possessed great dexterity in such arts, and requested him to try it; he drew a tree with oil varnish and colours on a plate of glass, applied the acid on the plate in the usual manner; after it had been upon the plate for a sufficient time, poured off, and the plate afterwards cleaned of the varnish, a beautiful tree was left bright and smooth, with a rough back-ground. It is conceived that many great improvements may yet be made in this process.
It appears that no other acid than that produced by the sparry fluor is capable of corroding every kind of glass, though Baume, in his “Chemique Experimentale,” says, that many kinds of glass may be corroded by the marine and vitriolic acids.
In this state of uncertainty was the public mind till the year 1725, when it was thought that a recipe, older than that previously mentioned, might possibly be discovered. Accordingly, in that year, in the month of January, the following is said to have been transmitted to the publisher of the “Œkonomische Encyclopedie,” by Dr. John George Weygand, of Goldingen, which is reported to have belonged to Dr. Matthew Pauli, of Dresden, then deceased; with which the last named gentleman had etched, on glass, arms, landscapes, and figures of various kinds. We find, that in it, very strong acid of nitre was used, which entirely disengages the acid of sparry fluor, though the vitriolic acid has been commonly employed, and figures thus produced will appear as if raised above the plane of the glass.