Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1873-05-28

may be printed.
Beside this, the common printing-types,
though made of metal, are not nearly 50
hard as copper, and in constant use they
soon wear out but when these types have
been once made ready for printing page
of book or a newspaper, electricity will,
in the same way as with an engraving,
make for us precise copy of the page, in
the same hard metal, from which as many
impressions as are usually wanted can be
struck off. Not only this, but the same
wonderful force will spread very delicately
over the face Of common printing types a
thin, but very hard, coating of copper,
which makes them last much longer than
they will without it.
In these ways electricity not only brings
us knowledge quickly from all parts of the
world, but helps to make our books and
newspapers cheaper and handsomer than
they would otherwise be.
Lightning sometimes makes pictures on
the skin of persons who are struck by it.
The electrotyping process is somewhat
similar. Those pictures are supposed to
be made by the lightning. in sudden dis
charges, tearing off particles of the sur
face which it leaves, carrying them through
the air. depositing them on the surface of
the next object to which it passes, or which
it is said to strike. But in electrotyping
the gentle, steady current of battery is
employed.
First, quantity of copper is dissolved
in sulphurc acid (oil Of vltrioD, contained
in large tub or trough. Copper will dis
solve in this acid very much as salt or SUI
gar will melt in water. A plate or sheet
of copper is suspended on metal rod in
this trough, to keep up the supply. The
liquid thus prepared is called copper
bath.
Next. mold is taken Of the wood en-
craving or page of types Of which copy
is desired, by pressing it upon beeswax
gutta- percha, or some other soft material.
This mold receives, of course, an exact
impress Of every line, however delicate, in
the object to be copied. But wax and
gutta.percha are non-conductors of cleo
tricity, so nothing can be done with this
mold until it is in some way made con-
ductor. This is done by covering its sur
face very carefully with finely powdered
plunbago, or black lead, the same that
your black-lead pencils are made of other
wise called graphite), which is good con.
ductor of electricity. All loose particles
of this are carefully brushed or blown off,
and then the mold is suspended in the cop
per bath, face to face with the plate Of
copper, but several inches from it.
Then the copper plate is connected by
wire with the positive pole of an electric
battery, and the mold with the negative
pole. A current of electricity at once
passes through the liquid, causing the fine
particle of copper to be slowly deposited
on the surface of the mold, nicely filling
every part and line. These particles ad-
here frml y together, making very hard
coating of solid metal, When this coat.
ing has become about the thickness of a
sheet Of tin, which requires not more than
two or three hours, the mold is removed,
and then the copper presents face which
is an exact engraving or type which was
impressed on the wax.
But this thin layer Of copper, called a
" SHE'LL cannot be used to print from. A
quantity of melted metal, chiefly lead, il
then poured upon the back of it, which
fills every part. and, when cooled, adhere:
6rmTy. After trimming, the whole form
4 solid plate somewhat less tia one fourth
of an inch in thickness. Til is is what i
called an electrotype plate, and when fas
tened upon block of wood of the proper
height it is ready for the printers use.
Stereotyping is a different process, ii
which electricity is not used. The wore
stereotype means a firm or solid type. t
make stereotype plates, the ordinary print
ing-types are set and prepared as for cleo
trotyping; then mold is taken of then
in a paste made by mixing ground plaster
ot-paris with water. This soon DRIES, anC
is baked until well hardened, Then
quantity Of type-metal is poured into thi
, mold, and this, when cooled, presents
complete copy Of the types from which tn
mold was formed, in one solid plate
Wood cuts can be copied in the same way
But the type metal, though harder tina
wood, is not as hard as copper, and vii
% not wear nearly SO long. Stereotypn
T has been in use for many years, and was
, great Improvement when first invented.
costs somewhat less than the electrotyp
- process, and serves we'll where there ar
= no fine eDgravlngs, and where but fe
thousand copies are TO be printed.-Oa
Young Folks.