26 EXTERNAL WALL FINISHES Living green copper
NEW INNOVATIONS IN SURFACE TREATMENTS, AS WELL AS IMPECCABLE ENVIRONMENTAL CREDENTIALS, ARE SET TO INCREASE THE ARCHITECTURAL USE OF COPPER CLADDING - AS GRAEME BELL, FROM INTERNATIONAL METALS SPECIALIST LUVATA UK, EXPLAINS.
C
opper is one of the few materials that can offer the designer complete material continuity and real freedom of form, and the installer ease of workability at any temperature. It is extremely durable with an indefinite lifespan and no maintenance requirement. In particular, copper has impeccable environmental credentials, including well-established recycling practices, recognised in the current BRE ‘Green Guide to Specification’ which includes various A+ and A rated copper- finished roof and wall cladding specifications.
Distinctive Patina In terms of architectural design, the natural development of copper patina is one of the material’s unique characteristics, with colours changing from bright copper to dark brown and eventually to the distinctive green seen on older copper roofs. This patina takes time to develop – from around 7 years in coastal climates to 10 years or more in urban areas and up to 30 years in clean environments. It is dependent on various factors including the presence of air-borne pollutants and the ‘dwell-time’ of rainwater on the surface. So in some situations, such as sheltered vertical facades, it may never appear at all, leaving a dark brown oxidised surface instead.
To address this issue, various patination treatments have been developed in recent years to provide straightaway a green surface similar to the natural process. Generally, these treatments have involved either factory pre- patination, where sheet sizes have had to be limited, or on-site application of copper compounds after installation. But a unique process developed by international metals specialist Luvata has transformed this
technology to offer complete flexibility for both new-build and renovation projects. The Nordic Green PLUSTM process is carried out in the factory on a dedicated production line under carefully controlled conditions. Here, pre- oxidised copper is sprayed with specifically formulated copper compounds to create the desired patina colours and heat treated to chemically bind them to the copper.
Living Surfaces The process can be accurately controlled so that, as well as the solid green patina colour, other intensities of patina flecks can be created revealing some of the dark brown oxidised material behind. These Nordic Green PLUSTM ‘Living’ finishes can be adjusted to meet the architect’s specific requirements, creating exciting design opportunities on new
buildings or matching existing naturally patinated copper for refurbishment. In marine climates, the natural copper patina contains some copper chloride giving it more of a blue colour and this can be emulated with Nordic Blue PLUSTM using the same process, including the capability to provide varied intensity Living Blue finishes. This major innovation offers architects unparalleled design freedom and the ability to control the type and intensity of patina. Of particular importance is that there are no limitations on the length of pre-patinated copper sheet or strip used on a project because whole coils are treated on the production line, not just limited size sheets.
Now, for the first time, designers can determine specific pre-patinated copper surfaces for use in long-strip and other larger-scale installation techniques. This development also opens up a wide range of cladding possibilities not previously achievable. For example, horizontal or vertical bands mixing different surface patination intensities have been used to create beautiful striated facades on buildings around Europe and Scandinavia, and now in the UK as well. In addition to this important development with pre-patination, other surfaces are available today including pre-oxidised copper with either light or dark brown oxidisation to both faces that otherwise takes time to develop in the environment. Copper alloys are also popular for cladding including Brass and Nordic RoyalTM- an alloy of copper and aluminium with a long- lasting golden colour.
Further information is available on
www.luvata.com/architectural
Luvata UK Click here to request literature
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