Printing and writing materials : their evolution by Smith Adele Millicent

Author:Smith, Adele Millicent
Language: eng
Format: epub, pdf
Tags: Writing -- Materials and instruments, Printing -- History, Papermaking, Bookbinding
Publisher: Philadelphia : Smith
Published: 1904-03-25T05:00:00+00:00

As the mould comes out uneven, it has to be built up; this is done by filling the large blank spaces and the surfaces between the lines with hot wax, so that the deposits of copper may be shallow. The mould is then given a coat of graphite in the black-leading machine. The graphite makes the mould a conductor of electricity.

After the deposit of this metallic surface, the superfluous graphite is washed out by water. Iron filings are then sifted on the mould and a weak solution of sulphate of copper is stirred in. This coating of copper is given to facilitate the plating. To make the electrical connection, a piece of copper or lead is imbedded in the edge of the sheet of wax.

The mould is then suspended for one or two hours in a bath of sulphate of copper solution. By the action of the electric current, the coating is increased until it is about .005 of an inch thick.

The shell of copper is removed from the wax and is washed in boiling water. It is brushed on the back with a solution of chloride of zinc, and sheets of tinfoil are laid over it and melted. Enough molten lead is pom-ed on the shell to give it the necessary thickness—about one-eighth of an inch. An air-blast causes the plate to cool and solidify immediately.

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