Building with metal: metals have been used in buildings for more than three millennia. What were originally rare and honorific architectural substances are now essential, and their potential is incalculable. (Comment).

Our use of metals is as old as civilization -- indeed the two are intimately connected, for metal cannot he worked from ore without sophisticated social and economic structures. And without metals -- copper, bronze, lead and iron -- we would still have to make do with tools of stone and wood, and could scarcely have set out to tame the world as we have done. Bronze (the alloy of copper and tin) was the initial key to commanding large scale, fine wrought construction (copper itself' was too soft to make much impact on stone -- though the Pyramids were probably built with copper and stone tools).

So it is in some ways surprising that until about two and a half centuries ago, metals played a rather small part in making building fabric (as opposed to the tools with which it was made). In Greek and Roman times, metals were used almost only honorifically: as decoration in for instance the metal acroteria of some Hellenistic temples, and in the gilded bronze plates of the Pantheon's roof and portico (the latter only finally wrenched off in the early seventeenth century by the the Barberini pope Urban VIII to make Bernini's baldacehino in St Peter's -- hence the comment Quod non fecerunt barbari, fecerunt Barberini). In medieval times, churches and cathedrals were often roofed in lead, easy to extract and work. And clecoratiotis (at least for the tombs of the rich) were often made in glittering brass -- the alloy of copper and zinc, in some ways a substitute for gold: a shiny substance which has been used in the same way into our own times. Almost pure copper clad the marvellous early Renaissance green spir es of northern Europe but, like lead, it was not suitable for other purposes than protection from the elements. Zinc too was a chadding its greyness giving calm coolness from the roofs of Switzerland to the bar tops of Paris.

Metal was rarely used structurally until the Industrial Revolution, when the mass production of iron (cast and wrought) became possible through developments in ore refining and metal processing. Cast iron gave us slenderness in compression. Before the easy production of poured iron, compression had to be clean with by large masses of masonry. Suddenly it was possible to carry heavy loads almost transparently. Wrought iron greatly multiplied the possibilities of tension: much wider roof spans than those offered by timber alone were now possible. Steel, cheaper to produce than very labour intensive wrought iron, transformed the world. Wrought iron was endlessly hammered by artisans to make commonplace material into a strengthening substance. Its main purpose was to produce sharp and bendable weapons. Steel produced the great train sheds of European railway stations, skyscrapers in America, the Galcric des Machines at the 1889 Paris Expo and the Eiffel Tower at the same time.

Metals explode

In the nineteenth century the French, basing their work on British Industrial Revolution prototypes, developed a new form of construction that combined masonry (usually brick) with iron and steel. The marvellous invention of the jack arch (a combination of brick vaulting stiffened by wrought iron or steel beams and often supported on cast iron columns) allowed new perceptions of mass carried apparently effortlessly -- potentially as powerful a spatial device as the dome floated over Hagia Sophia by Isodorus of Miletus and Anthemios of Tralles. The jack arch reached its artistic apogee in the 1960s in the viscerally moving St Peter's church, Klippan, Sweden by Lewerentz.

In the twentieth century, uses of metals in building increased exponentially, in both applications of familiar substances and the introduction of new ones. Aluminium for example, though one of the commonest elements, was a precious metal until the end of the nineteenth century, and was used largely decoratively for a decade or two after it was possible to smelt the metal economically (think for instance of Otto Wagner's ornamental cast aluminium bolt heads at the 1906 Post Office Savings Bank in Vienna). But suddenly, aluminium became one of the most important of building materials, relatively resistant to corrosion compared with steel, lightweight and cheap, it became the great cladding material of the mid twentieth century, the extruded anodized metallic component of millions, of curtain walls. Aluminium has had a bad time, because the canonical buildings in which it was used are now unfashionable, it is very expensive in energy terms to extract, but its obviously useful properties will doubtless reassert t hemselves: perhaps it needs a new Wagner to show radical ranges of possibilities.

Metals proliferate. Frank Gehry is titanium's Wagner. His Bilbao Guggenheim showed the potential of a seemingly incorrosible material, flexing shiny in the sun. Stainless steel is now relatively cheaper than it was even a few years ago, and its applications in building are becoming manifold, as Heikkinen & Komonen show in this issue with their adaption of the stainless-steel mesh made for supermarket conveyor belts into a translucent veil for their community centre at Vuotalo (p40).

Other new elements, alloys and applications will doubtless be invented. The potential of metals for climate modification is just beginning to be explored. Our main task as a profession is to reduce consumption of energy in buildings, both in construction and running. Metals offer many possibilities for climate control, ranging from lightweight movable louvres to elaborate electronic photo-responsive devices, the potential of which we are only beginning to glimpse. Since the first cast iron bridge was built at Coalbrookdale, Shropshire in 1779 (in some ways a masonry structure realized in another material) the potential of metals in construction has immeasurably increased.

We cannot now say what the architecture of the future will be like, but it is quite clear that metal components, lightweight, capable of, instant adaption and able to respond quickly to the moods of climate, are vital elements of new ways of building that we can only dimly comprehend. The light-weight, adaptable qualities of metals will complement the thermal and acoustic properties of mass: masonry, concrete or even earth. The new architecture will, somehow, be an orchestration of the dancing high notes of metal components and the deep perecussion bass of the heavy bits. It is up to us to write the score.