Of Printing From Cavities
83. The art of printing, in all its numerous departments, is
essentially an art of copying. Under its two great divisions,
printing from hollow lines, as in copperplate, and printing from
surface, as in block printing, are comprised numerous arts.
84. Copperplate printing. In this instance, the copies are
made by transferring to paper, by means of pressure, a thick ink,
from the hollows and lines cut in t
e copper. An artist will
sometimes exhaust the labour of one or two years upon engraving a
plate, which will not, in some cases furnish above five hundred
copies in a state of perfection.
85. Engravings on steel. This art is like that of engraving
on copper, except that the number of copies is far less limited.
A bank-note engraved as a copperplate, will not give above three
thousand impressions without a sensible deterioration. Two
impressions of a bank-note engraved on steel were examined by one
of our most eminent artists,(1*) who found it difficult to
pronounce with any confidence, which was the earliest impression.
One of these was a proof from amongst the first thousand, the
other was taken after between seventy and eighty thousand had
been printed off.
86. Music printing. Music is usually printed from pewter
plates, on which the characters have been impressed by steel
punches. The metal being much softer than copper, is liable to
scratches, which detain a small portion of the ink. This is the
reason of the dirty appearance of printed music. A new process
has recently been invented by Mr Cowper, by which this
inconvenience will be avoided. The improved method, which give
sharpness to the characters, is still an art of copying; but it
is effected by surface printing, nearly in the same manner as
calico-printing from blocks, to be described hereafter, 96. The
method of printing music from pewter plates, although by far the
most frequently made use of, is not the only one employed, for
music is occasionally printed from stone. Sometimes also it is
printed with moveable type; and occasionally the musical
characters are printed on the paper, and the lines printed
afterwards. Specimens of both these latter modes of
music-printing may be seen in the splendid collection of
impressions from the types of the press of Bodoni at Parma: but
notwithstanding the great care bestowed on the execution of that
work, the perpetual interruption of continuity in the lines,
arising from the use of moveable types, when the characters and
lines are printed at the same time, is apparent.
87. Calico printing from cylinders. Many of the patterns on
printed calicos are copies by printing from copper cylinders
about four or five inches in diameter, on which the desired
pattern has been previously engraved. One portion of the
cylinders is exposed to the ink, whilst an elastic scraper of
very thin steel, by being pressed forcibly against another part,
removes all superfluous ink from the surface previously to its
reaching the cloth. A piece of calico twenty-eight yards in
length rolls through this press, and is printed in four or five
88. Printing from perforated sheets of metal, or stencilling.
Very thin brass is sometimes perforated in the form of letters,
usually those of a name; this is placed on any substance which it
is required to mark, and a brush dipped in some paint is passed
over the brass. Those parts which are cut away admit the paint.
and thus a copy of the name appears on the substance below. This
method, which affords rather a coarse copy, is sometimes used for
paper with which rooms are covered, and more especially for the
borders. If a portion be required to match an old pattern, this
is, perhaps the most economical way of producing it.
89. Coloured impressions of leaves upon paper may be made by
a kind of surface printing. Such leaves are chosen as have
considerable inequalities: the elevated parts of these are
covered, by means of an inking ball, with a mixture of some
pigment ground up in linseed oil; the leaf is then placed between
two sheets of paper, and being gently pressed, the impression
from the elevated parts on each side appear on the corresponding
sheets of paper.
90. The beautiful red cotton handkerchiefs dyed at Glasgow
have their pattern given to them by a process similar to
stencilling, except that instead of printing from a pattern, the
reverse operation that of discharging a part of the colour from a
cloth already dyed--is performed. A number of handkerchiefs are
pressed with very great force between two plates of metal, which
are similarly perforated with round or lozenge-shaped holes,
according to the intended pattern. The upper plate of metal is
surrounded by a rim, and a fluid which has the property of
discharging the red dye is poured upon that plate. This liquid
passes through the holes in the metal, and also through the
calico; but, owing to the great pressure opposite all the parts
of the plates not cut away, it does not spread itself beyond the
pattern. After this, the handkerchiefs are washed, and the
pattern of each is a copy of the perforations in the metal-plate
used in the process.
Another mode by which a pattern is formed by discharging
colour from a previously dyed cloth, is to print on it a pattern
with paste; then, passing it into the dying-vat, it comes out
dyed of one uniform colour But the paste has protected the fibres
of the cotton from the action of the dye or mordant; and when the
cloth so dyed is well washed, the paste is dissolved, and leaves
uncoloured all those parts of the cloth to which it was applied.