The artist’s lieutenant

Tony Cragg’s glass sculpture was put together by assistant John McCormack.

It is a little-known fact that most major international artists have a team of assistants to help them co-ordinate diary-defying media requests, public appearances and a relentless schedule of exhibitions worldwide.

This secret world of lieutenants was made public two years ago when British artist Julian Opie advertised in the Guardian for an assistant. He was swamped with 500 replies and the newspaper ran a follow-up feature.

It might seem scandalous that Damien Hirst pays somebody to produce his spot paintings for him, but this has been going on for a long time. Michelangelo started out painting frescos for another artist; Salvador Dali signed blank canvases for assistants to work on; and Andy Warhol made it a feature of his work that it could be mass-produced factory-style, leaving a legacy of confusion among collectors.

Although not as common here, artists wanting to produce ambitious, time-consuming work and meet the demands of the market will find they will eventually need more than one pair of hands.

British sculptor Tony Cragg last week opened one of the biggest projects realised by a British artist, featuring more than a dozen bronze works - weighing an estimated 47 tonnes - installed in the new 1.6ha extension of the Cass Sculpture Foundation's West Sussex estate.

Only five days before, an exhibition of six weighty Cragg works opened at Auckland's Gow Langsford Gallery. Cragg dispatched an assistant to spend a few days overseeing the installation.

A book documenting the Cass project will be published later this year and will no doubt mention John McCormack, who has been working with Cragg for 12 years, allowing him to confidently make decisions on the artist's behalf.

A towering stack comprising thousands of glass implements looks complex, but there is no specific arrangement to reproduce. McCormack has seen Cragg create it numerous times so has an instinctive sense of how he would do it himself.

"I know the sort of feeling he wants to get from it," McCormack says. "It's just a case of getting it to work aesthetically from every angle - trying to make it look good, basically."

As part of a team of about 12 assistants working in Cragg's studio, McCormack has an intimate knowledge of the works' complex shapes and construction.

He describes the pieces from Cragg's Early Forms series as being like morphing a pig into an elephant and finding out what happens in between. Although these look like the product of computer modelling, they have an energetic gestural quality as if they have been effortlessly stretched and twisted by a giant pair of hands. McCormack confirms that the cast forms in the exhibition were all hand made.

The twisted portraits began as cut-out silhouettes placed on angles and joined with layers of polystyrene ovals, which are carved and coated in resin before being sent to the foundry for casting.

The other pieces were similarly created from full-size models in plaster or polystyrene, with some cunning mould-making to create the reversed letters that line the exterior of Formulation.

After completing an art degree in Ireland, McCormack spent several years working at the German foundry that produces Cragg's bronzes, which is how he came to work for him.

Also an exhibiting artist, McCormack says he only expected to be with Cragg for a few years before striking out alone, but he is enjoying his present position, which has him jetting around the world.

He says it is important to keep his own work separate from the work he does with Cragg. "If there is somebody who's constantly throwing their own ideas at the art, it is very hard for the artist to concentrate on what he's doing."

Historians of British art have often discussed the lineage from Henry Moore to Anthony Caro, who began as Moore's assistant. McCormack admits that Cragg's ideas have also seeped into his own thinking. "There are similarities, obviously, because I've been working with him so long, so it influences what I do in my subconscious. I don't think about it when I am doing it but afterwards, when I look at it, I realise that could have come from there. But that doesn't bother me."

Exhibition

* What: Tony Cragg, Recent Sculpture
* Where and when: Gow Langsford Gallery, to June 4