Wednesday, 09 September 2020 10:30

Copper – Inside and Out

    Copper has seen a dramatic change from its historic place in roofing prestigious buildings to a thoroughly modern external skin for contemporary architecture. But its role as an interior surfacing material for homes and commercial building is growing as well, with a surprising diversity of natural colours, patterns and textures, says Graeme Bell, Nordic Copper Sales & Marketing Manager at Aurubis.

    Copper and its alloys – such as brass and bronze – enjoy a long heritage as the metals of choice for interior design, contributing a distinctive tactility to door furniture and handrails, and a visual richness to lighting and other fittings, championed by leading designers such as Tom Dixon. But increasingly, copper and its alloys are being applied as high-quality finishes for walls, doors, ceilings, elevators, highlight surfaces, bars, splashbacks and counters, exploiting the material’s unique performance characteristics.

    Safe surfaces

    Particularly important today, copper’s inherent antimicrobial qualities make it ideal for touch surfaces. It is also non-toxic and safe to handle, as well as non-brittle and predictable to work. With a melting point of 1083˚C and ‘A1 (non-combustible material)’ fire classification to EN 13501-1, copper is inherently fire-safe and, therefore, rated ‘Class 0’ surface spread of flame, making it suitable for wall and ceiling surfaces in communal areas. But there is more to architectural copper than meets the eye, particularly in terms of recyclability, sustainability and long-term performance, wherever it is used.

    Copper’s exceptional longevity – conservatively regarded as 200 years – is due to the patination process which ensures extreme durability without maintenance and resistance to corrosion in virtually any atmospheric conditions. This natural development of a distinctive patina when used externally defines the material, with colours changing over time dependent upon local environmental conditions and air quality.

    Within a few days of exposure to the atmosphere, the surface begins to oxidise, changing its colour from a ‘bright’ mill finish to chestnut brown, which darkens over several years to a chocolate brown. Continued weathering can eventually result in the distinctive green or blue patina seen on older roofs. Obviously, copper used internally and away from the outside environment will not change and develop in this way.

    Living material

    Modern factory-applied surface treatments can provide straightaway oxidisation and patination of copper surfaces to a selected level, which can also be used internally. Essentially, they bring forward the environmental changes without taking away the integrity of copper as a natural, living material and are not coatings or paint. Some of the processes involved are very similar to those taking place in the environment and utilise copper mineral compounds, not alien chemical actions.

    These processes can enable designers to determine both the colour and intensity of patina for each project from the start. As well as a solid patina colour, other intensities can be created revealing some of the dark oxidised background material as ‘living’ surfaces. Alloys of copper have also grown in popularity. They include bronze, an alloy of copper and tin which gradually changes to a dark chocolate brown when used outside, and brass, which can also be supplied pre-weathered. An innovative alloy of copper with aluminium and zinc enjoys a rich, golden through-colour which remains very stable, just developing a matt surface – but no patination – over time.

    Surface treatments

    Most recently, these copper surfaces and alloys have been made available with a diversity of mechanically applied surface treatments, adding an extra dimension. The latest developments in abraded and embossed mechanical surface treatments are particularly suited to interior design, adding another level of close-up visual richness, texture and tactility. These treatments include embossing to provide regular patterns of raised or recessed forms, some also abraded to reveal highlights of the base material colour for additional design effects. Grindings are also available with linear, cross-hatched or curved-swirl hairlines to give distinctive matt surfaces.

    These surface treatments, combined with the natural living colours of copper and its alloys, offer real design freedom, adding a richness and opulence to public areas. They can also provide an inherent warmth and sense of quality to highlight surfaces in homes as well.

    Forms and systems

    Apart from traditionally-jointed, rolled material supported by a substrate, various other forms of copper are increasingly being explored by innovative designers. For example, copper can be supplied in profiled sheets or extremely flat honeycomb panels, and it can be pressed to provide surface textures and modulation. The material can also be perforated, expanded or woven as mesh giving varying degrees of transparency. When used internally, of course, copper can be used in an even wider range of forms and systems, free from the constraints of weather-proof detailing.

    One particular recurring architectural theme is material continuity, blurring the boundaries between outside and in with external copper cladding simply continuing past fully-glazed walls. When used outside, it’s important to remember that ongoing changes to copper, including pre-oxidised and pre-patinated, as well as alloys such as brass and bronze, will continue over time depending on the local environment. Again, this does not generally apply to interior applications, and designers should understand and, indeed, celebrate the divergent developments of internal and external copper.

    Finally, it’s worth remembering that the creative use of copper externally can have a major impact on the interior of a building as well. In this boutique hotel, external screens of copper tiles arranged in chevron patterns add a distinctive Art Deco feel internally. The mixture of perforated and opaque copper tiles – and their selective omission – curate views to the city, as well as modify daylighting and reduce glare.

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