Colouring

Colouring of materials is an art in itself and is often the most important factor in a customers choice of materials, in particular for architectural components. On bronze this is carried out by controlling the patina, which is a film on the surface of bronze or similar metals produced by oxidation over a long period or otherwise induced.

Here at EDL Architectural Metalwork we have years of experience in the control of patina and the process of patination and can work closely with clients to establish the perfect finished colour, as required, wether its simply for surface protection or for a particular aethestic.

Patinas & Patination

The patina protects and passivates a material against corrosion. This natural patina is solid and seldom shows a tendency to flake. There are a variety of different effects can be created by the use of different chemicals and waxes etc.. Some typical effects are shown in the chart below (pictures courtesy of Copper Development Association).

Exposure to chlorides leads to green, while sulfur compounds such as liver of sulfur tend to brown. The basic palette for patinas on copper alloys includes chemicals like ammonium sulfide for blue-black, liver of sulfur for brown-black, cupric nitrate for blue-green and ferric nitrate for yellow-brown. For artworks, patination is often deliberately accelerated by applying chemicals with heat. Colors range from matte sandstone yellow to deep blues, greens, whites, reds and various blacks. Some patina colors are achieved by the mixing of colors from the reaction with the metal surface with pigments added to the chemicals. Sometimes the surface is enhanced by waxing, oiling, or other types of lacquers or clear-coats.

Repatination

Damage to an items patination can cause corrosion to the bronze beneath as well as appearing unattractive. We can undertaken repatination of both small and large areas for repair and restoration purposes.