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COMMENT
COMMENT Timeless architectural copper
Copper continues to intrigue and inspire architects. With limitless possibilities for innovative contemporary design, copper also provides exemplary recyclability, sustainability and longevity explains Chris Hodson from Aurubis
A
s one of our oldest building materials, copper’s unique, timeless architectural qualities are defined by its naturally changing patina – which cannot be successfully replicated using other materials with surface coatings. The patina film provides impressive protection against corrosion and can repair itself if damaged, giving it exceptional longevity. Within a few days of exposure to the atmosphere, a copper surface begins to oxidise, changing from the ‘bright’ mill finish to a chestnut brown, which gradually darkens over several years to a chocolate brown.
Developing visual characteristics
Continued weathering can then result in development of the distinctive green patina – or blue in coastal locations. This process is an expression of the metal’s propensity to revert to mineral compounds that resemble the ore from which it originally came. Some rainwater is needed for the patina to form and its rate of development will depend on the water “dwell time” on a surface. As a result, vertical cladding and sheltered surfaces will take much longer to patinate naturally than exposed roofs. Airborne pollution also increases the rate of patination, which therefore takes longer in more remote, cleaner environments than in cities or industrial areas. The complex combination of factors determines the nature and speed of development of patination, giving copper unique, living visual characteristics developing over time in response to local conditions.
Natural material Today, factory-applied surface treatments can provide oxidisation and patination of copper straight away to a selected level. This is particularly useful for vertical surfaces which might not otherwise ever develop a blue/green patina. The processes involved are very similar to those taking place in the environment – not alien chemical reactions. They bring forward environmental changes without taking away the integrity of copper as a natural, living material.
These surface treatments form an integral part of the copper and are not coatings or paint. They utilise the same brochantite mineralogy found in natural patinas all over the world. Oxidisation can be light or dark, and with pre-patination the process can be
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TEACHING AND LEARNING CENTRE FOR BIRKBECK, UNIVERSITY OF LONDON A theatrical rooftop extension, clad in copper, announces the new teaching and learning centre for Birkbeck, University of London © Timothy Soar
ADF OCTOBER 2022
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