As soon as the plate shows the slightest change, or the copper begins to reappear, the coating of steel is removed by chemical agents, which, acting differently on the two metals, corrode the one, while they leave the other untouched. The plate is thus brought back to its original state, and is therefore in the same condition as before to receive a second steel-facing. In this way plates may be de-steeled and re-steeled a great many times, and the proofs printed from them may be carried up to considerable quantities.
As a rule, the plates are not steel-faced until after the proofs before lettering have been printed.
Soft-ground etchings, the biting of which is quite shallow, must be steel-faced after two to three hundred impressions.
The delicacy of the bur thrown up by the dry point hardly permits the printing of more than twenty or thirty proofs on an average; steel-facing carries this number up to a point which cannot be fixed absolutely, but it is certain that the bur takes the steel quite as well and as solidly as an etched line. Dry points may, therefore, yield long editions; the steel-facing must in that case be renewed whenever necessary.[26]
100. Copper-facing Zink Plates.—Zink plates cannot be steel-faced, but they can be copper-faced.[27] Steel-facing has been adopted by the Chalcographic Office of the Louvre, and by the Gazette des Beaux Arts, that remarkable and unique publication which is an honor to criticism and is found in all art libraries. Steel-facing, in fact, is universally employed; it preserves in good condition the beautiful plates of our engravers, and makes it possible to put within reach of a great many people engravings of a choice kind, which but lately were found only in the salons of the rich and the collections of passionate amateurs.
An Etcher's Studio.
From the Third Edition of Abraham Bosse's “Treatise,” Paris, 1758.
Pl. IX.