There was a figure stooped over a can of Dulux High Gloss paint when I entered the Upper Gallery of Modern Art Oxford. Drips of grey paint ran down the outside of the can. Two paintbrushes, a screwdriver and a bottle of paint thinner added to the detritus on the floor. Had it been a real door, no doubt the painter would have hung a Wet Paint notice on the door handle before turning his back on his workmanship. But it wasn't and he didn't.

The figure adding that Turneresque finishing touch to his work was Gary Hume - the exhibition featuring 18 of his works is entitled Gary Hume: Door Paintings, inspired by the swing doors at St Bartholomew's Hospital. They are the foundational works in his oeuvre. More than 50 Door Paintings make up the entire series and this exhibition offers us a chance to view the most significant ones created during the 1980s and early 1990s, along with three works dated 2000/2001 and 2006.

Walk into the Piper Gallery and you will be forgiven for thinking that all you see are a series of large canvases covered in domestic magnolia paint. Actually, there's much more to them than that. Hume's Magnolia Door series, completed in 1989 and Door (Brown), which he did a year earlier, are the first of his Door Paintings. They set up a formula, a schemata of a double swing door with two porthole windows. Painted on the traditional support canvas with thickly applied gloss paint, the kick-plate motifs are barely visible when first viewed.

Hume is an artist who admits to never actually painting light, but wants to have light in the pictures, which is why he spent hours sanding the surface of those early canvases to create as sleek a support as possible.

Later he began working on MDF panels and a double-layered Perspex to get this effect. His more recent works are painted on polished aluminium panels. These can be seen in the Upper Gallery and include Black Door With Sash, All He Knows and Shine.

Works such as the double panelled Girl boy, boy girl of 1990/91 clearly depict the port holes and kick-plates in bold contrasting colours with such slickness it would be easy to imagine that a real pair of doors were hanging on the gallery wall.

This exhibition continues until August 31.