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.
[Illustration: COPPERPLATE PRINTER.]