They may look like prostitutes' calling cards, but on a canvas by Sarah Stewart, they're art, reports Fiona Mountford
If, late one night, you should see someone lurking around the phone boxes of Soho, tampering with the "business" cards inside, don't assume the worst. It could just be American artist Sarah Stewart, collecting material for her latest project.

"I've always looked at these cards and thought they could make interesting paintings, because from a distance they look really nice, colourful pictures, but up close they're a lot more disturbing," she says. After mulling the idea over for a couple of years, she finally set to turning the (inducements to) pornography into art, by collaging them onto canvases and painting resin over the top to give them a plastic sheen.

The results of this experiment were shown at her two recent London exhibitions, and if sales are anything to go by, they were extremely successful. (Buyers of previous work include Mick Jagger, Pedro Almodovar and Rifat Ozbek.) She has sold more than 100 pieces, ranging from 10in by 14in to 4.5ft by 4.5ft. "Someone bought that big one for his dining room," she laughs, "but people buy most of them as presents or to put in their loos." In the face of increasingly vigilant attempts to remove the cards from public places, Stewart's work could become, as she puts it, "a piece of London history you can have as art".

She is quick to point out the woman-hours involved in scouring the less salubrious areas of London for her material. Whereas a big picture necessitates collecting hundreds of these cards - "And they have to be good ones" - to cut-and-paste in best Blue Peter fashion, even a small canvas requires up to 30. Luckily, she has a willing network of friends and clients (in the arty sense of the word, of course) who hoover up possible samples for her.

However, she did have one rather unfortunate encounter with two old ladies who watched her hard at work in a phone box near Green Park. "I came out and they said, 'You filthy girl, taking other people's cards and only leaving your own.'" Stewart's next project will see her gathering the recently introduced "business cards" of Paris. It's certainly one excuse to tour the world.