The wax mould being built, is ready for blackleading, to give it a
conducting surface upon which the metal may be deposited in the bath,
superfluous blacklead being removed with a bellows. Blacklead, being
nearly pure carbon, is a poor conductor, and a part of the metal of
the pan is scraped clean, to form a place for the commencement of
the deposit. The back of the moulding is waxed, to prevent deposit of
copper thereon, and the face of the matrix is wetted to drive away
all films or bubbles of air which may otherwise be attached to the
blackleaded surface of the type.
The mould is then placed in the bath, containing a solution of
sulphate of copper, and is made a part of an electric circuit, in
which is also included the zinc element in the sulphuric-acid solution
in the other bath. A film of copper is deposited on the blacklead
surface of the mould; and when this shell is sufficiently thick, 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.