Visiting Thea Djordjadze's new apartment in Berlin last spring, I came across a strange blue-green object on her bedroom windowsill. It was a curious shape - a half sphere, with a complex crisscross pattern embossed on the curved surface. It was about the size of my hand and looked like a coral specimen from a natural history museum, except that it was the colour of oxidised bronze. Unable to resist touching it, I picked it up. The thing had a flat and smooth underside, onto which a serial number had been written in black pen in Djordjadze's hand, which gave me to understand that this was an artwork. It was lighter than I had expected, and made not of some mineral substance but of moulded plaster. The grooves in the striated curved surface felt lovely to touch in comparison to the cool flatness of the base. Still no closer to understanding what the thing was, I carefully replaced it on the windowsill.

That evening Djordjadze mentioned how several of her recent works had been damaged by gallery visitors seemingly incapable of withstanding the impulse to touch or re-arrange them. The previous autumn, when she was still living in Cologne - where she had been based since 2001 - she twice had to travel back to Berlin to repair Deaf and Dumb Universe (2008), her work for the Berlin Biennial. Spectators had repeatedly poked and prodded the work's chair-like sculptures, which were made of sponge covered in plaster and paint; she showed me a photograph of the surface of one piece that was pitted with fifteen depressions made by other people's fingers. A few months