ick, it
is taken from the bath, the wax removed, the shell trimmed, the back
tinned, straightened, backed with an alloy of type-metal, then shaved
to a thickness, and mounted on a block to make it type-high.
A RECENT IMPROVEMENT.
has been introduced in which there is added finely pulverized tin to
the graphite for facing the wax mould; the effect in the sulphate of
copper bath is to cause a rapid deposition of copper by the
substitution of copper for the tin, the latter being seized by the
oxygen, while the copper is deposited upon the graphite. The film is
after increased by the usual means. Knight's expeditious process
consists in dusting fine iron filings on the wet graphite surface of
the wax mould, and then pouring upon it a solution of sulphate of
copper. Stirring with a brush expedites the contact, and a
decomposition takes place; the acid leaves the copper and forms with
the iron sulphate a solution which floats off, while the copper is
freed and deposited in a pure metallic form upon the graphite. The
black surface takes on a muddy tinge with marvelous rapidity. The
electric-connection gripper is designed to hold and sustain the
moulding pan and make an electric connection with the prepared
conducting pan of the mould only, while the metallic pan itself is out
of the current of electricity, and receives no deposit.
BACKING-UP.
The thin copper-plate, when removed from the wax mould, is just as
minutely correct in the lines and points as was the wax mould, and the
original page of type. But it is obvious that the copper sheet is no
use to get a print from. You must have something as solid as the type
itself before it can be reproduced on paper. So a basis of metal is
affixed to the copper film, and this again is backed up with wood
thick enough to make the whole type-high. To get this, a man melts
some tinfoil in a shallow iron tray, which he places on the surface
of molten lead, kept to that heat in square tanks over ordinary fires.
The tinfoil sticks to the back of the copper, and on the back of this
is poured melted type-metal, until a solid plate has been formed, the
surface of which is the copper facsimile and the body white metal. The
electro metal plate, copper colored and bright on its surface, has now
to go to the
FINISHING ROOM.
Here are two departments. In one the plates are shaved and trimmed
down to fit the wood blocks, which are made in the other department.
Some of these operat
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