Precious metal: a new era of bespoke systems of structure and cladding is testing metals and architectural imagination to their limits.

The Machine Age was the golden age of metals. Constituting both the means and end to production, machine tools and the goods they produced during the past 150 years fundamentally changed the way we live. Consumer society, for better or worse, was nourished on a diet of metal products ranging from fridges to Fords. In architecture, the steel frame and the enormous tensile capability of steel spawned both high-rise and long-span structures that radically transformed the scale and character of the built environment. The concept of doing more with less emphatically combined aesthetic ideas and industrial efficiency--themes made manifest, perhaps symbolically, in the structures produced in Britain that celebrated the new millennium.

However, the concept of lightness is changing. As Italo Calvino observes, 'The second industrial revolution, unlike the first, does not present us with such crushing images as rolling mills and molten steel, but with "bits" in a flow of information travelling along circuits in the form of electronic impulses. The iron machines still exist, but they obey the orders of weightless bits.' (1) As in all areas of our lives, the processes of design, fabrication and assembly of metal structures and cladding are being dramatically altered by these weightless bits. Gehry's Bilbao Guggenheim (AR December 1997) fired the public imagination of an architecture for the future. However, even though its design and fabrication were made possible by software, the rationale of its construction belonged to the old world of standard rolled steel sections and modular cladding systems. The Experience Music Project (EMP) (AR October 2000), completed just three years later, albeit superficially like Bilbao, was built using very different processes. It belongs to the new order of complex bespoke systems in which every structural and cladding component is unique.

Further evidence of the paradigm shift is provided by Foster's Swiss Re (AR November 2003), Toyo Ito's Sendai Mediatheque (AR October 2001) and OMA's Seattle Library (AR August 2004) which, like Bilbao, straddle the boundary between the machine and digital ages, using standard rolled steel sections in variable structures. While in Swiss Re, the system that changes incrementally from floor to floor can be readily perceived and understood. Sendai and Seattle are preoccupied with creating the appearance of instability and replacing overarching rational systems with what Cecil Balmond calls 'improvised connectivity'. (2)

Liberating cladding

Considering cladding, in addition to the effect of 'light' digital design and fabrication processes, the move from sealed systems to the rainscreen is having a profoundly liberating influence. Instead of the literal opacity of sealed systems with their cumbersome folded seams, top hat sections and gaskets, the open jointed rainscreen with its separate waterproofing membrane behind provides enormous freedoms for designers, which they are exploiting to different conceptual and practical ends.

In the hands of Herzog & de Meuron--whose work has transformed the perception of many materials--metal rainscreens become delicate perforate veils. The copper bands of their early Signal Box 4 Auf dem Wolf--which both become three-dimensional and transform from sealed to perforate through rotation from vertical to horizontal--were ostensibly designed to function as a Faraday cage as well as a visual screen. More recently, the expanded aluminium mesh cladding of the extension to the Walker Art Center (AR January 1989) and the copper cladding of the De Young Museum (p46) have less to do with technical performance and more to do with appearance and perception. Both are carefully judged explorations of the balance between standard panel sizes that conform to the old economy of mass production and complex surface treatments made feasible by digital production. Although the bas relief surface patterns of both buildings initially appear random, each has an underlying system. The Walker's distinctive wrinkled skin is created by random rotation of a single pattern created by a good old-fashioned metal stamping dye, while the De Young's patterning--perforated and stamped--oscillates between abstraction and image, having been derived from a dot screened photograph.

Perhaps most provocative in the rich ambivalence between palpable materiality and thin abstraction--perhaps even surface decoration--is OMA's recent work with metals. On the one hand is their unbuilt proposal for San Francisco Prada, which in contrast to both the Modernist separation of structure and skin and the current fascination with the multilayered rainscreen--developed a perforate and sealed stainless-steel skin that also worked as a structural diaphragm. Instead of a kit of parts, it was monolithic; instead of repetition, it was a variable system to have been fabricated by CNC (computer numerical controlled) water jets; in place of the desire for thinness as an index of efficiency, it was emphatically thick. On the other hand, in the new concert hall in Porto (AR August 2005), super-thin super-scaled pixellated gold leaf cross-dresses as wood grain on the plywood lining of the auditorium.

In the recent work of Morphosis--notably the Caltrans Headquarters in LA and the Federal Office Building in San Francisco (both AR July 2005)--the metal wrapper literally takes on a life of its own. Here, the thin scrim is manipulated three-dimensionally with greater freedom than the watertight volumes it veils. Conceived as a 'metabolic' skin, it performs as a key component of the buildings' environmental systems, which are designed to reduce energy consumption and advance sustainability. Thom Mayne notes, 'In lieu of a conventional mechanical plant, the building actually "wears" the air conditioning like a jacket.' (3)

With another agenda, the cast bronze facade of the Museum of American Folk Art (AR February 2002), by Tod Williams Billie Tsien & Associates, uses the same rainscreen principle to create a surface pitted with craters and fissures--unpredictable imperfections from the fabrication process that contrast markedly with the smoothness of Gehry, the controlled patterning of Herzog & de Meuron and, looking to the past, the machined precision of the Seagram Building, a bronze-clad icon just a few blocks away. MAFA's metal cladding, although perforate, differs in significant ways. With panels ranging from 6 to 16mm in thickness, this bronze skin is neither actually nor apparently light. It was not digitally fabricated but instead was cast at a sculptors' foundry, aiming to reinstate the imprint of human craft--or what David Pye called the 'workmanship of risk'--in contemporary construction. (4)

These preoccupations are driven by digital design and CNC cutting, stamping and welding, with weightless bits enabling machines to create the appearance of craft, almost without human intervention on the shop floor. In contrast with the formerly arduous process of 'tooling up', the A. Zahner Company, which has fabricated metal cladding for both Gehry and Herzog & de Meuron, is fleet-footed, moving rapidly through generations of software as they seek to handle complexity more efficiently. As an example, they note that each of the 3600 unique cladding panels of the EMP required an average of 250 megabytes of data and a design time of 2.5 hours. On more recent Gehry projects, this has been reduced to 30 megabytes and 15 minutes per panel. (5) As always in construction, time has cost implications. With constant scrutiny aimed at streamlining process, Henry Ford's principle of minimising labour is being energetically applied, not only on the shop floor, but also to the human content of CAD-CAM technologies themselves.

This streamlining has been well suited to an economic environment in developed countries that, during the past thirty years, has seen relatively modest increases in metals prices but rapidly escalating costs for labour. Suddenly the equation is changing with the cost of steel, copper and other metals skyrocketing in response to the insatiable appetite of China's developing economy combined with the effect of both war and weather on the price of oil. Will metals continue to provide fertile territory for the exploration of form, performance and perception, or will global economic pressures render the use of metals in architecture a luxury?

1 Italo Calvino. Six Memos for the Next Millennium, New York: Vintage International, 1988, p8.

2 Cecil Balmond. 'New Structure and the Informal', Architectural Design, Sept-Oct 1997, p88.

3 A Model of Excellence--The New Federal Building, Washington DC: US General Services Administration, p26.

4 David Pye. The Nature and Art of Workmanship, Cambridge University Press, 1968, pp4-8.

5 Interview with William Zahner, A. Zahner Company, 2002.