IF YOU are within sight of Edinburgh Castle this Friday night you would be well advised to look to the skies. Edinburgh will be presenting its very own war of the worlds in the shape of a triple-decked rainbow of black fireworks against the blue evening sky from renowned international artist Cai Guo-Qiang.
That is, of course, if it all goes to plan. Gunpowder is, after all, an inherently unstable material. But the element of unpredictability is part of this New York-based artist's signature explosive work. Cai's explosions, from Projects for Extraterrestrials in Japan to the spider's web of fireworks for the 250th anniversary of the British Museum, are vast and awesome. But Cai is not just a big bang provocateur, although he enjoys the stagey effect, a residue, perhaps, of his university training in theatre design. His works are more related to that first Big Bang and the idea of other intangible worlds, real or supernatural. He brings the dark matter of the universe up close, with decidedly less destructive consequences.
There are, however, dark roots. Born in 1957, Cai was brought up during the violence of the Cultural Revolution; it was not until he left for Japan in 1986 that he gained artistic freedom and inspiration. Although he has never returned to live there, this year he curates China's first Pavilion at the Venice Biennale, where, incidentally, he won the Lion D'Or in 1999. A spiritual homecoming perhaps for a man who says he has the outlook of a nomad.
Despite his international recognition, it is the reception of the work that is causing a quiver of concern in Edinburgh. In the wake of the London bombings, there are worries that noisy explosions over the castle may be misinterpreted. The police, apparently, are anticipating panic calls, much as they do at New Year.
"There is a political interpretation to my works, and connotations of the shadow of terrorism; it is something I have been inspired by since moving to New York," says Cai, who is staging the explosions series in three parts - the first in Valencia earlier this year, the third in Beijing in the autumn. "I think people will perhaps now more easily grasp the focus of the specialised ideas of the black rainbow. Although there are connotations of fear in daytime, the black rainbow has a more universal context. When the explosions are finished, the smoke forms a big cloud, which you can interpret as a dark cloud over your head. It has an uncomfortable quality." It is a symbol of hope, blackened.
Cai's impact on the Scottish capital will not just be a momentary intervention on the city skyscape. The Fruitmarket Gallery is mounting a major exhibition of his works in collaboration with the Edinburgh Art Festival, and Cai will also be exhibited at the Scottish National Portrait Gallery. Gunpowder still features, this time on a more intimate level.
Exploded on special paper, Cai's "gunpowder portraits", specially made for Edinburgh, will feature 12 historical Scottish figures associated with crime or the paranormal. At the Portrait Gallery, three will be exhibited alongside a number of portraits specially selected by Cai from the gallery's substantial holdings and chosen with the aid of Scots novelist James Robertson, who has written some new ghost stories, especially for the exhibition.
Excerpts from these will inscribed, along with Chinese ghost stories, on the leaves of a plantain palm - a tree said to attract ghosts in China - installed at the Fruitmarket. The trees will be filmed on CCTV overnight, and replayed during the day for gallery visitors.
For a man who has always been interested in the 'extraterrestrial', without believing in ghosts "but believing in the possibility of other worlds", it is not surprising that Cai decided to work with the city's supernatural history. He points out that the dark side of Edinburgh, "a city of stories relating to the unseen", is something strongly promoted by its tourism.
"It is fascinating the way the city council treats the ghost stories as a cultural treasure for the city," he says. "I've been on several of those Edinburgh ghost tours for my research. Like the city council, I am making an art work out of the dark side of Edinburgh."
Black Rainbow above the Castle, Friday, 7pm; The Fruitmarket Gallery (0131-225 2383), Saturday until September 25