From Xylographs to Lead Molds; A.D. 1440-A.D. 1921 by H. C. Forster

Author:H. C. Forster [Forster, H. C.]
Language: eng
Format: epub
Tags: History, General
ISBN: 9781505985733
Google: d-3EDwAAQBAJ
Goodreads: 27022430
Publisher: Createspace
Published: 2015-07-17T00:00:00+00:00

Table of Contents

An electrotype is a facsimile printing plate duplicated from an original. The original may be either type, a woodcut, a zinc or a copper etching such as a line-cut or a half-tone, or it may be a combination of type-matter and line-cuts or half-tones.

We commonly think of electrotypes as printing plates made of copper, but any metal which can be electrochemically deposited may be used. Because of their wearing qualities and economy, however, copper and nickel are the two metals commercially used for electrotyping.

Briefly, an electrotype is made by taking an impression of the original in a plastic substance, thus forming a mold or matrix; depositing copper or nickel on the mold; removing the copper or nickel shell from the mold and backing it with a semi-hard metal; trimming the metal to printing-plate thickness, and bevelling, or blocking on wood, the trimmed plate for printing-press use.

In modern practice more than twenty-five different operations are necessary to make a finished electrotype ready for the press. They may be enumerated, as follows:

Case-making. The flowing of a molding compound composed of “ozokerite,” a resinol-mineral wax, onto the case. The case is of copper.

Flashing the Case. Passing a flame over the surface of the melted ozokerite immediately after flowing the case in order to remove air- bubbles.

Case-shaving. The automatic shaving of the top surface of the flowed case after the ozokerite has hardened to give it a smooth, even surface for molding.

Graphiting. Brushing surface of case with molding graphite to prevent the pattern from sticking to the wax mold.

Molding. Making an impression from the original zinc line etching, half-tone or type form in the waxed case. This is done by means of a hydraulically operated molding press.

Cutting-down. The levelling off by hand, using a sharp trowel shaped tool, of the splurge after the impression has been made. Flashing is also used here to remove the burr left around the letters after the cutting down process.

Building-up. The adding of wax by hand to the blank spaces in the molded case so that in the finished electrotype they will be well below the printing face.

Black-leading. Making the face of the molded case electrically conductive by applying graphite.

Stopping-out. Insulating with a thin coating of wax the edges and back of the copper case to prevent copper being deposited except on the face of the mold.

Pumping-out or Oxidizing. Coating the face of the molded case with chemical copper to hasten deposition of copper shell in the bath.

Deposition of Shell. The molded case is put in the electrolytic bath for the deposition of shell thereon.

Releasing Shell from Molds. Stripping the deposited shell from the waxed mold by dashing hot water on it. The wax is melted off case and used again.

Washing Copper Shell. Hot lye-water or steam is used to clean off any wax sticking to it.

Trimming Copper Shell. Rough edges of shell outside the guard line trimmed off.

Aciding Copper Shell. An application of fluxing medium to back of copper shell so that tin will adhere.

Tinning Copper Shell.

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