Behind the innocent line "this exhibition would not have been possible without the generosity of the Victoria and Albert Museum" by the door to the National Gallery's show Art of Light, thrums the purr of curatorial agendas. When the V&A opened in 1852, London's public collections were divided in two: roughly, the National Gallery got paintings, the Prince Consort's new Wunderkammer got sculpture and craft. Stained glass is craft: so what is an exhibition of German Renaissance windows doing at the National?
The answer, or part of it, is that the line between craft and art has shifted in time. Luca della Robbia was an artist, even when he worked in ceramic; Raphael designed tapestries. Since Ruskin, though, craft has become art's poor relation, made by people in smocks and marked by the stigma of function. Grayson Perry's pots - art masquerading as craft - pick up on this shift. Even more troublesome is stained glass - its function is spiritual, and fine artists have long involved themselves in its making. Showing monastery windows alongside paintings by masters such as Dürer raises questions about where craft stops and art starts.
That, at least, is the thinking behind Art of Light, which hangs paintings by Dürer and Hans Baldung Grien next to works in stained glass more or less influenced by them. That there was any crossover at all between the two media is a point worth making; that the traffic might not have been all one way is even more arresting. The period covered by the show - the years either side of 1500 - was one of extraordinary energy in the visual arts of northern Europe. The quasi-alchemical colour experiments of glass makers would certainly have appealed to painters such as Baldung, as would the colours themselves. Equally, the notion of painting as a finestra aperta - an open window on a parallel world - was an old one in European aesthetics. Art that was made to be put in windows was bound to intrigue. The illusionist faux-stone frame of the Master of Cappenberg's panel, Christ before Pilate, suggests the appeal of stained glass to painters, as do the work's saturated colours and segmented composition.
All this is interesting, but where Art of Light falls down is in its belief that hanging works side by side makes them equal in the history of art. At the turn of the 16th century, German painters were struggling to free themselves from the archaisms of International Gothic, an anti-humanist mode still visible in the unbodily drapery of Baldung's The Trinity and Mystic Pietà. Stained glass was deeply - perhaps inextricably - rooted in the Gothic, the aesthetic of cathedrals. The tessellated surface of a stained glass window, all action broken down into lead-edged patches of colour, worked against the naturalism that the period's genius, Albrecht Dürer, was busy making fashionable in Nuremberg. You have only to compare Dürer's drapery with Baldung's to see which way the wind was blowing, and it was not in the direction of stained glass.
What happened next was predictable enough. Whatever novelties painters may have taken from glass-makers, painting became the unquestioned senior partner in the pictorial arts of the church. One problem, achingly obvious in the candle shown in the window of Tobias and Sarah on their wedding night, was the suggestion of cast light, a vital part of the repertoire of any self-respecting <U>Renaissance</U> painter. And then there was the intractable bugbear of lead. By the time an anonymous German glass-maker came to copy Dürer's Ecce Homo in the mid-16th century, the leading strips of his window creep across the composition as though apologising for their existence. Whoever made the glass copy of Dürer's The Virgin as Queen of Heaven in 1530 or so solved this problem by omitting lead altogether. The resulting work is very pretty, but it stretches taxonomy to call it stained glass. It is the glass reproduction of a painting, which is a different thing.
As often with the National's Sunley Room shows, Art of Light is incisive, clever and small. I can't help feeling, though, that it is trying to do something unwieldily big, which is to redraw the line between art and craft or do away with it altogether. (The V&A would certainly approve.) What it actually ends up doing is reinforcing the old-fashioned idea that craft and art are irreconcilably different, and that the second is better than the first; something of an own goal, when you think of it.
Art of Light: German Renaissance Stained Glass, National Gallery, London WC2 (020 7747 2885) to 17 February
Further reading 'The Autumn of the Middle Ages' by Johan HuizingaReuse content