Color Effects on Metal Using Ferric Chloride

Etchant

• The purpose of an etchant is the removal of part of a metal. The reason for the removal can be artistic or commercial, such as a printed circuit board. An artist makes a design on a copper plate. An etchant like ferric chloride removes the unwanted copper by its corrosive effect. This allows the artist's design to be highlighted. Etching with ferric chloride, in effect, changes the appearance of the copper.

Intaglio

• Etching, also known as intaglio, is a process that involves dipping a copper plate into a solution of ferric chloride. Lines have been drawn on the plate prior to dipping. The amount of time necessary for the etchant to work depends upon the strength of the solution and its temperature. The longer the plate remains in the ferric chloride solution the deeper the etch lines. The artist determines how deep to make the lines based upon his concept of the finished plate. Use a small test plate before exposing your plate to the solution.

Etchant Color

• In addition to altering the copper plate, ferric chloride changes color as it interacts with the copper. The ferric chloride starts off a reddish brown and then turns a darker brown. The appearance of the dark brown indicates the effectiveness of ferric chloride. It does its best work when dark brown. Once it turns a dark green or black it no longer is working. It is time to halt the process and use new ferric chloride if further etching is required.

Damascus Steel

• Knife makers use Damascus steel. Part of the process in making a knife involves etching with ferric chloride. Etching turns the steel blade a darker color. The longer the time in the solution the darker the blade. Watch the blade; it is silver if not etching and becomes darker as the etching continues. Remove the blade when it reaches the desired color and texture.