The Green Dream of pre-oxidised copper as an aesthetic choice for cladding

Over the Rainbow

Whether it conjures up fond memories from your childhood – or makes you cringe every time you hear Judy Garland crooning Somewhere Over the Rainbow – most people I know have some recollection of The Wizard of Oz. In 1939 the movie adaptation of L. Frank Baum’s popular books hit theatres and ever since has been a fixture on ‘greatest film’ lists. For those in need of a refresher… when a cataclysmic twister deposits her farmhouse in the middle of Munchkin Land (and atop the Wicked Witch of the East) young Dorothy Gale begins a quest to return to Kansas – because after all, “there’s no place like home”. With the yellow brick road to guide her, and joined by a plucky Scarecrow, a melancholy Tin Man, and a Cowardly Lion, Dorothy and co set off to see the Wizard, with the vengeful Wicked Witch of the West in hot pursuit.

The film took full advantage of newly developed colour motion picture technology which allowed the story’s most iconic elements – such as the ruby slippers and the yellow brick road – to leap from the screen in glorious Technicolor. Audiences were wowed by a spectacle which truly encapsulated the rainbow Dorothy pines for in the hit song. For me personally, the image that resonates the most is that of the Emerald City – the glistening, green edifice that is home to the Wonderful Wizard of Oz. I guess its towering form appeals to my architectural sensibility!

Emerald City

Throughout the film the Emerald City looms as the final destination for Dorothy and her friends and signifies the place where dreams can be realised. The city itself is a place of benevolence and sanctuary, and with that in mind the choice of emerald green as the defining colour is fitting. In emerald lore, the precious stone is said to be restful on the eyes, and the colour green – traditionally representative of nature and renewal – is known to induce feelings of calm. For this reason, green interiors have remained a popular choice for decorators throughout the ages. But despite being the dominant colour in the natural environment, building exteriors have typically preferred a palette of warm browns and greys true to stones, earth and timbers. In construction, naturally derived materials have been perennial favourites, but this need not limit colour selection despite long- standing trends. The Periodic Table’s family of metals can deliver a rainbow of natural hues, and one in particular is worth a shout-out…

Copper – the Unheralded Rainbow of the Periodic Table

Copper has long been a favourite among designers for its warm, lustrous finish. Its other attributes include high resistance to corrosion, low thermal movement, and its light weight making it a popular choice for roofs, gutters and flashing. Newly fabricated copper components are notable for their brilliant orange appearance that quickly changes when exposed to oxygen… and herein lies its appeal! Copper and its alloys (such as bronze and brass) over time build-up a surface layer of oxide- sulfate – known as ‘patina’ – that provides a protective coating over the copper surface underneath. Depending on its chemical composition, copper alloys will typically change colour from a bright, lustrous orange, through a spectrum of reds and browns, and ultimately to grey/green once the copper surface is fully oxidised.

Keen to be Green

Historically considered the province of the elite, copper has traditionally been reserved for use in distinguished buildings and crowns the domes of cathedrals and government institutions the world over. Once aged – and no longer displaying its distinctive warm tones – architectural copper can easily go unrecognised. Show of hands… who knew that the Statute of Liberty is copper clad? Increasingly an appreciation for copper in its end state has led to the production of pre-aged copper in our impatience to achieve the alluring blue-green tones that the material would otherwise take many years to adopt.

Chemically induced patina can be achieved through the application of acids to the metal to fast-track the patination process and better control factors such as uniformity and colour quality. Its appeal is broadening, and increasingly we are seeing the appearance of pre-aged (or pre-oxidised) copper on the pages of ArchDaily and Dezeen. Steven Holl’s Sarphatistraat Offices in Amsterdam, and Gensler’s Fourth Presbyterian Church in Chicago are two outstanding examples of the material in contemporary public architecture. At the St Lawrence Chapelin Vantaa, Finland, Avanto Architects incorporated copper panels pre-patinated by hand to striking effect in the ceiling of the chapel. Contrasting with crisp, white plasterboard walls, a dark stone floor, and blonde timber pews and paneling, the mottled green ceiling is evocative of a protective tree canopy stretching over the small congregation beneath. The material palette is rich in metaphor, and the combination of colours and textures is one of the most beautiful I’ve seen in a house of worship.

There’s No Place Like Home

Materials in architecture are less likely than ever to be used to distinguish between social strata or differentiate between private and public buildings. Nowadays, the humble homeowner can clad their house in the very same products that shroud a civic landmark. On a Sunday stroll not long ago through the leafy streets of Melbourne’s north-east, a pop of green on the side of a house caught my eye. Further inquiry revealed the residence in question to be Eaglemont House by Kennedy Nolan Architects. The green was – as you may have gathered – pre-aged copper sheet. It crossed my mind whether the material selection had been driven by the client, or if they had been persuaded by an enthusiastic designer with a green dream! The latter I understand was the case.

The homeowner was keen for robust finishes that would withstand the years and retain their quality. The surrounding landscape is densely planted and no doubt this leafy context inspired a colour selection that was both sympathetic and distinctive. Whilst green may not have been the client’s immediate choice, the architect reports that they responded well to the suggestion. I can only assume that the family now in residence must feel their enterprise rewarded by a superb new home that is both bold and completely at one with its surroundings.

No doubt this little emerald palace is the much-anticipated destination of a visionary client who has been delivered a home that will support a growing family over the years and patina in sympathy with the aging landscape around it.