Century Dictionary and Cyclopedia
- n chemitype A process for obtaining casts in relief from engravings. A polished zinc plate is covered with an etching-ground, on which the design is etched with a point and bitten in with dilute aqua fortis. The etching-ground is then removed, and every particle of the acid well cleaned off. The plate is covered with filings of a fusible metal, and heated until the metal has melted and filled the engraving. When cold it is scraped away to the level of the zinc plate in such a manner that none of it remains except what has entered the engraved lines. The plate is next submitted to the action of a weak solution of muriatic acid; and, as the one of these metals is negative and the other positive, the zinc alone is eaten away by the acid, so that the fusible metal which has entered the hollows of the engraving is left in relief, and may be printed from in a press. Chemitype is particularly adapted for the production of maps.
Chambers's Twentieth Century Dictionary
- n Chemitype kemi′-tīp the chemical process for obtaining casts in relief from an engraving