Inspiring Architects with Copper’s Sustainable Contributions to the Building Construction Market
Buildings covered with copper can be admired for decades and even centuries.
There are many examples of historical buildings, palaces and churches all over Europe with their green copper roofs and gutters proving copper to be both beautiful and durable.
Contemporary architecture also benefits from copper, because it complements commonly-used materials such as brick, wood, stone and glass and can be used for buildings with traditional or modern styles. In addition, copper meets the important requirements of state-of-the-art building design, which demands recyclable and sustainable materials. In existing legislative framework, the production and use of copper products generally safeguards the environment and citizens of Europe, where about 45% of copper demand is met using recycled resources.
Copper is a beautiful material: no other metal, except gold, has a colour; when exposed to the environment its shiny red becomes brown and then progresses to its distinctive green patina. Industry is now able to provide pre-oxidised and pre-patinated sheets to architects, who appreciate the availability of forms (solid sheet and strip, punched, meshed and more) and their ability to be easily shaped.
Copper alloys have entered modern architecture in the last few decades; bronzes, brasses and copper-aluminium are increasingly used for buildings, especially for facades, thanks to their appealing look and their long life.
Copper, and copper alloys, give performance, durability (100+ years), a range of colours, forms and textures, all in a natural, infinitely recyclable material.
Copper sheets are fixed with clips, some fixed and some sliding, which allow the copper to expand and contract with changes in the temperature. If the copper is fixed rigidly then splits in the sheet may occur.
The high copper brasses (gilding metals) such as CuZn10, CuZn15, CuZn20 and CuZn30 have a range of colours and are well suited for this application. Obtain samples to find the exact colour.
For handrails which come into contact with the public, the best protection would be given by periodically waxing using a natural wax such as Carnauba or beeswax. For rails which are only subject to atmospheric attack a lacquer such as Incralac should be used.
This alloy has been widely used for some notable contemporary statues since it patinates easily and is capable of being deformed to remove any distortion produced on casting. However, since no current standard exists for this alloy there might be a problem since the public has access to the structure, so it is suggested that leaded gunmetals CC491K (LG2) or CC492K (LG4) are used.
Brasses will slowly oxidise (tarnish) in the atmosphere; outdoors the process is more rapid due to the effect of moisture, salt (in marine environments) and pollutants such as sulphur dioxide (acid rain) in industrial areas. The tarnishing can be greatly delayed and the range of colours, which give copper alloys their aesthetic appeal, maintained by either lacquering or waxing (or both).
Lacquering: one of the most effective lacquers is Incralac. Lacquers must be applied in dry, factory conditions and are not suitable for protecting components which are handled by the public, such as handrails, since acid levels of moisture in the skin (pH 5.5) damage the lacquer.
Waxes: copper alloys may be more cheaply protected by waxing. It is important to use natural non-reactive waxes such as Carnauba or Beeswax, not synthetic waxes which will eventually granulate and absorb water. Natural waxes are not affected by UV light.
- Remove surface oxide with dilute (10%) hydrochloric acid
- Neutralise with bicarbonate solution (lye)
- Seal by chromate conversion
- Clean with detergent annually.
The first job is to clean the surface. Use a detergent with a kitchen scouring sponge (usually green). For a badly stained surface it may be necessary to incorporate pumice powder with the detergent. For large areas it may even be necessary to shot blast the surface. After cleaning, dry the surface with hot air and as soon as possible wax the surface using natural wax. Natural wax is essential since it will enhance the true colour and form a protective coating, repelling water. Artificial wax should not be used since it will crack in time and draw water in.
Yes, it has been used for many years. However the nitrous oxide fumes given off when absorbed into surrounding fabric create a fire hazard. Also energy is used in the heating process. Better to patinate cold or use prepatinated copper.
A clear acrylic resin finish containing tarnish inhibitor. It is an air drying ester lacquer containing Benzotriazole, a corrosion inhibitor. It can be relied upon to provide protection for 3-8 years outdoors and for much longer indoors.
Aerial views of contemporary copper architecture in London