THE COPPERPLATE ENGRAVER.
1. The engravers on metallic surfaces are termed copperplate engravers, not because copper is the only metal on which they exert their skill, but because it is the one on which they usually operate. The plates are prepared for the artist by the coppersmith, by rubbing them with brickdust and charcoal, after having cut them of a proper size from sheets of copper.
2. The instruments employed by this artist are few and simple, the principal of which are, the graver, the dry-point, the scraper, and the burnisher. The graver is a small bar of steel, of a square or lozenge form, and, with the short handle into which it is inserted, about five inches in length. One of the angles of the bar is always on the under side of the instrument, and the point is formed by bevelling the end from the upper side, or angle. The square form is used for broad strokes, and the lozenge for fine ones.
3. The dry-point, or needle, is a steel wire with a long cylindrical handle; or it is simply a wire of sufficient length and size to be used without a handle. The scraper has nearly the form of a triangular pyramid; and the cutting part, which has three edges, is two or three inches long. The burnisher has a form nearly conical, and, without the handle, is about three inches long. The last two instruments are frequently made of the same piece of steel, properly forged at each end. In such case, the middle part of the steel is the handle by which they are held.
4. Of engraving on copper, the following are the principal varieties or styles: 1. Line engraving; 2. Stippling; 3. Etching; 4. Mezzotinto; 5. Aquatinta. For the purpose of conveying some idea of these different branches, we will describe them under distinct heads.
5. Line engraving. The first thing done, in this species of engraving, is to transfer to the plate an exact copy of the outlines of the design to be executed. In accomplishing this, the plate is moderately heated, and covered with a thin coating of white wax. A piece of transparent paper is then laid over the design to be copied, and traced in outline with a black-lead pencil. The outline thus sketched is turned down upon the coating of white wax, and the whole is subjected to the action of a rolling-press; or it is kept for a while under heavy weights. By the application of this pressure, the lines are transferred from the paper to the wax on the plate in a reversed position, which is necessary to make the impression of the finished plate resemble the original.
6. The pencil-marks on the wax having been lightly traced on the copper with the dry-point, and the wax having been melted off, a perfect outline is found on the plate. Small subordinate parts of the design are transferred to the plate in the same manner, except that the transparent paper is brought in forcible contact with the waxed surface by means of the burnisher.
7. At this stage of the process, the artist commences the use of the graver. While operating with this instrument, he holds the handle in the palm of his hand, and pushes the point forward with a firm and steady motion, until a line is produced by a removal of a portion of the metal. By a succession of such strokes, judiciously applied, the work is completed. The burrs, or little elevations of the copper, left by the graver on each side of the lines, are removed by means of the scraper and burnisher. Mistakes or blemishes are erased from the plate, either with the burnisher, or by friction with charcoal.
8. Stippling. The second mode of engraving is called stippling. This resembles the last method in its process, except that the effect is produced by means of minute punctures or excavations, instead of lines. These are made either with the dry-point or graver. When produced by the former instrument, they are of a circular form; when by the latter, they are rhomboidal or triangular. This style of work is always more slow, and consequently more expensive, than engraving in lines. It has, however, some advantages in the softness and delicacy of its lights and shades, and the prints struck from it approach more nearly to paintings.
9. Etching. This mode of engraving is far more easy than any other, being performed chiefly by chemical corrosion. In fact, any person who can draw, may etch coarse designs tolerably well, after having learned the theory of the operation. To perform it, the plate is first covered with a thin coating of some resinous substance, upon which the acid employed can have no action. The design, and all the lines it requires, are next traced on the plate with steel points, called etching needles, which are instruments similar to the dry-point.
10. The second part of the process is the corrosion, or, as it is technically called, biting in. This is effected by pouring upon the design a quantity of diluted nitric acid, after having surrounded the edges of the plate with a wall of soft wax, to prevent the escape of the fluid. A chemical action immediately takes place in all the lines or points where the copper has been denuded by the needle. After the first biting has been continued long enough, in the judgment of the operator, the acid is poured off, and the plate examined.
11. The light shades, if found sufficiently deep, are then covered with varnish, to protect them from further corrosion. The biting is then continued for the second shades, in the same manner, and afterwards, for the third and succeeding shades, until the piece shall have been finished. The plate having been cleaned, and carefully examined by the aid of a proof impression, the deficiencies which may be discovered are supplied with the graver.
12. Mezzotinto. In the production of this kind of engraving, the whole surface of the plate is first roughened, or covered with minute prominences and excavations too small to be obvious to the naked eye; so that an impression taken from it, in this state, would present a uniform velvety, black appearance. This roughness is produced mechanically by means of a small toothed instrument, called a cradle.
13. When the plate has been thus prepared, the rest of the process is comparatively easy. It consists in pressing down or rubbing out the roughness of certain parts of the plate, with the burnisher and scraper. Where strong lights are required, the plate is restored to a smooth surface; for a medium light, it is moderately burnished, or partially erased; and, for the deepest shades, the ground is left entire, and sometimes etched, and corroded with nitric acid. Impressions from mezzotinto plates approach more nearly to oil paintings than any other prints. This kind of engraving was invented by Prince Rupert, in 1649.
14. Aqua-tinta. There are several methods by which this kind of engraving can be executed; we, however, will describe the one which seems to be the most simple and obvious. The outline of the picture having been etched or engraved in the usual manner, the surface of the copper is sprinkled equally with minute particles of rosin. This dust is fixed to the surface by heating the plate until the rosin has melted.
15. The ground having been thus laid, the parts of the plates not intended to be occupied by the design are stopped out by means of thick varnish. The plate is now surrounded with a wall of wax, as for etching, and diluted nitric acid is poured upon it. A chemical action immediately takes place, by which the surface exposed between the resinous particles is minutely excavated.
16. The lighter shades are stopped out at an early stage of the process, and the biting in is continued for the darker ones. After the plate is judged to be sufficiently corroded, it is cleansed, and an impression is taken on paper. The process is finished by burnishing the shades, to give them greater softness, and by touching up the defective parts with the graver.
17. This mode of engraving is well adapted to light subjects, sketches, landscapes, &c.; but, owing to the fineness of the ground, the plates wear out rapidly, and seldom yield, when of ordinary strength, more than six hundred impressions. The prints taken from such plates bear a strong resemblance to paintings in Indian ink, or to drawings in black-lead pencil. Aqua-tinta is the most precarious kind of engraving, and requires much attention on the part of the artist. It was invented by a Frenchman, named Leprince, who, for a time, kept the process a secret, and sold his impressions for original drawings.
18. Steel engraving. The process of engraving on steel plates differs but little in its details from that on copper plates; and the chief advantage derived from this method, arises from the hardness or toughness of the material, which renders it capable of yielding a greater number of impressions.
19. This mode of engraving was first practised, in England, by the calico-printers; but steel was first employed for bank-notes, and for common designs, by Jacob Perkins, of Newburyport, Massachusetts; and by him, in conjunction with Asa Spencer, of New-London, and Gideon Fairman, of Philadelphia, the use of steel in this application was generally introduced, not only in the United States, but also in Great Britain, some time before the year 1820.
20. The plates are prepared for the engraver from sheets of steel about one-sixth of an inch in thickness. A plate cut from a sheet of this kind is first softened by heating it with charcoal, and suffering it to cool gradually in the atmosphere. It is next planished, or hammered on a peculiar kind of anvil, to make it perfectly level, and afterwards ground on one side upon a grindstone. The operation is completed by polishing it with Scotch stone and charcoal. When steel was first substituted for copper, it was hardened before it was used in printing; but it is now used in its soft state, as it comes from the hands of the artist.
