One recent morning in Manhattan, Richard Serra watched the first 25-tonne fragment of his awesome installation, Intersection II, lifted in the garden of the Museum of Modern Art (MoMA). A few days later, models of even larger recent works were hoisted into the museum's galleries for a retrospective of 40 years of his sculpture that opened last month. The gap between plan and reality was closing, but it wasn't there yet.
Now 67, Serra seems to see himself more as an overseer of ideas than as a grappler with materials. 'I'm basically a model builder,' he says. 'I build models in lead and then we graph them out on a computer and send them to the factory in Germany.'
Pride of place in MoMA's new show is given to the torqued spirals, toruses and ellipses that have occupied him since the 1990s. Inspired by the architecture of a baroque chapel in Rome, they're huge expanses of Cor-Ten steel that flex even as they rise, creating dramatic impressions of bending space. They evoke the minimalism of the 1960s from which Serra emerged, their mottled surfaces reminiscent of the muscular painting of abstract expressionism. Those lucky enough to have seen a number of them installed in the Frank Gehry-designed Guggenheim Museum in Bilbao will appreciate that Serra has made his art echo and parallel some of the most inspiring architecture of recent times.
That alone would be enough for most artists' careers, but Serra has been innovating from the outset, his early work being seen as some of the first and most important examples of post-minimalism.
Where do the new ideas keep coming from? 'The work comes out of the work. Oftentimes the solution to one work leads to a different order of problems. For instance, when I was first working on casting pieces in lead - just splashing them into a corner and pulling them off - Jasper Johns saw one and asked if I'd build one for him. I had a sheet of lead with me that I wanted to melt down, so I shoved it in the corner, just bisecting the corner, and then I realised it was freestanding, and I thought, isn't that interesting.'
Although a contemporary of post-modernists, Serra is an old-fashioned modernist in the way he talks about materials. 'In the 1960s, materials kind of got dismissed,' he says. 'Things could just be written down. It didn't matter what the material was so long as you could describe it, but I thought, if you do something in glass, it's different than if you do something in paper, or wood or steel.
'So when I was trying to build these ellipses, all the architects told me to build them in concrete, but that wasn't the point - I needed the tightness of the band under compression to allow the gravity to bespeak of its matter.'