Artist: Georges-Pierre Seurat (1859-91), acknowledged leader of the post-impressionists and inventor of pointillism. He combined the ideals of academic French art with a curiously distant commentary on modern life - he said he wanted to paint people as if they were figures on the Parthenon frieze.
Seurat grew up in La Villette, on the outskirts of Paris. He decided young to become an artist, and fused classical values - he trained at the Ecole des Beaux-Arts under a pupil of Ingres - with self-taught optical science. He made his name with his proletarian pastoral painting Bathers at Asnières (1884), now in the National Gallery, which became an avant-garde icon after it was rejected by the Salon exhibition and shown at the alternative Société des Artistes Indépendants. He guaranteed his immortality with Sunday Afternoon on the Island of La Grande Jatte (1886), now in the Art Institute of Chicago. He died of a heart infection at the age of 31.
Subject: Madeleine Knobloch, Seurat's lover, a working-class woman whom he kept a secret almost throughout their relationship, not just from his bourgeois family but also from his bohemian friends. They had a child who died at the age of one, not long after his father. Knobloch was given some of Seurat's paintings as an inheritance but she cut off all communication with his family after his death.
Distinguishing features: In this portrait, painted circa 1889 to 1890, Seurat both teases and adores his lover, depicting her against conventional traditions of portrait flattery as comically out of scale to her tiny rococo dressing table. Some have seen it as cold, even misogynistic, in its portrayal of the falsehoods of cosmetics, or snobbish in its mockery of a working-class woman's attempts to be bourgeois.
But how wrong they are. This is a loving portrayal, almost out of control in its enthusiasm. The painter's unhinged involvement is revealed by the story that the bamboo frame on the wall originally contained a portrait of Seurat himself, until a friend warned him it looked bizarre. When the painting was shown in 1890, Knobloch's identity was concealed. Yet this is a radical announcement of individuality: she may be acting according to fashion but there's nothing bland about her hair piled up like a brioche, her downcast eyes, her strong face. Her curvaceous presence is a source of visual ecstasy. Seurat delights in her toilette even as he registers the comically disjunctive shapes of real life. Roundness abounds in a rhythmic dance: hairdo, breasts, arms, the folds of her dress.
Seurat has passed into history as the founder of a scientifically objective art movement, aiming to imitate the way light behaves in nature. Pointillism takes into account complementary colours in a painting surface that is a field of chromatically balanced "dots". While Seurat's imitators may have taken this theory absolutely seriously, the master himself used it as it suited him.
Seurat's field of dots is a medium of expression, nowhere more so than in the speckled universe that immerses Knobloch. The multitude of white and red flesh colours, gold, brown and violet, captures the nature not just of perception but of fantasy and feeling. There is no "wall", no "table", just forms shaping and reshaping. The wallpaper behind Knobloch, with its spiralling pattern, vibrates and expands like a soufflé. Seurat creates an aesthetic utopia he shares privately with his lover.
Inspirations and influences: Seurat's influences were the classicist Ingres, from whom he got his sense of structure - see Madame Moitessier (1856) in the National Gallery - and the romantic Delacroix, from whom he learned the power of colour. This painting jokingly plays the gravity of a neoclassical portrait against the frivolous archetypes of rococo art - the toilette scenes of Watteau and Fragonard. While Seurat's belief in experiment influenced modernism, the true nature of his art, its playful cannibalism of genres and expressive abstraction, was matched only by the greatest: Picasso, in Les Demoiselles d'Avignon (1907).
Where is it? Courtauld Gallery, Somerset House, London WC2 (020-7848 2526).