Copper and copper alloys are widely used in architectural applications to take advantage of their inherent range of colors. While these metals may be used in their natural color, as fabricated, it is sometimes desirable to chemically color pure copper (UNS C11000), commercial bronze (UNS C22000), architectural bronze (UNS C38500) or other alloys referred to as "bronze" in architectural parlance The most common colors to be produced are referred to as brown or statuary finishes for bronze and green or patina finishes for copper. This data sheet outlines procedures and formulations for producing both. While the chemical solutions described are those generally accepted in the metal finishing trade, many variations exist.
The wide range of colors and shades which may be achieved are largely a matter of craftsmanship and experience. Chemical coloring techniques depend upon time, temperature, surface preparation, mineral content of the water, humidity and other variables which influence the ultimate result. This data sheet presents the technology which underlies the craftsmanship and art involved in producing these colored finishes.
The standard designations for copper and copper alloys in the United States, the Unified Numbering System (UNS), are five-digit numbers preceded by the letter C. The current standard alloys by standard designation number along with their compositions can be found in the Copper Alloy Properties Database.