India paper (Chinese paper) promotes purity of line; but, as its surface is dull, it furnishes somewhat dry and dim proofs.
Japanese paper, of a warm yellowish tint, silky and transparent, is excellent, especially for plates which need more of mystery than of brilliancy, for heavy and deep tones, and for concentration of effect. Japanese paper absorbs the ink, and it is necessary, therefore, to bring up (retrousser) the plate strongly, and to wipe it with the rag. This paper is less favorable to sketches, the precise, free, and widely spaced lines of which accommodate themselves better to the tint of the laid paper.
Parchment may also be used for proofs; nothing equals the beauty of such proofs, printed either naturally, or wiped with the rag; they are the treasures of collectors.[24]
95. Épreuves Volantes.—On Chinese and Japanese paper, as well as on parchment, so-called épreuves volantes (flying proofs) are printed; that is to say, loose proofs, which are not pasted down on white paper. They are simply attached to Bristol board by the two upper corners, which brings them out perfectly.
96. Proofs before Lettering.—All of these various kinds of paper, each of which has its own claim for excellence, and especially Japanese paper, are by preference used for artists' proofs and proofs before lettering, which are printed before the title is engraved on the plate. It is customary to print a greater or less number of such proofs, which, being struck off when the plate is still quite fresh, show it at its best. After that, the plate is lettered, and an ordinary edition is printed from it.
It follows from this that the possessor of a proof without title has the best the plate can afford to give. But, as the pictures by the masters do not stand in need of a signature to be recognized, so the proofs before lettering may well do without the guaranty which is found in the absence of a title; even without this guaranty an amateur knows how to recognize the virgin freshness of an early impression, which is still further augmented by the extreme care bestowed on the printing of these exceptional proofs, but which cannot be kept up through a long edition.
97. Épreuves de Remarque.—Épreuves de remarque (marked proofs), showing the different states of the plate, and the various modifications which it underwent, are also sought after. Their rarity increases their price.[25]
98. Number of Impressions which a Plate is capable of yielding.—The number of impressions which a plate can yield is not fixed, as the power of resisting the wear and tear of printing depends largely on the delicacy or the strength of the work. The quality of the copper must also be considered, a soft plate giving way much faster than a hard plate which has been well hammered. The plates prepared to-day do not resist as well as those formerly made; and as the popularity of works of art multiplied by the press has considerably increased, it became necessary to look about for means by which the surface of a copper plate may be hardened, and be made to yield a large edition. This has been accomplished by
99. Steel-facing.—Steel-facing, which was invented by Messrs. Salmon and Garnier, and which M. Jacquin undertook to render practicable, consists in depositing a coating of veritable steel, by galvanic action, on the face of the copper plate, or, in other words, by the superposition of a hard metal on a soft metal.
This mode of protection, which perfectly preserves the most delicate passages, even down to the almost invisible scratches of the dry point, not only guarantees the copper against the contact of the hand and the rag, which would tell on it more than the pressure of the rollers, but at the same time makes it possible to print a thousand proofs of equal purity. Certain plates, owing to the manner of wiping used on them, do not reach this figure; others, more simply printed, may yield three to four thousand proofs, and sometimes even a still larger number.