I normally can’t stand hearing about the working habits of famous artists. Whether by sheer talent or some fiendish work ethic, they tend to be hyper-productive in a way that I could never be. Thankfully, there are counter-examples – like the painter Pierre Bonnard. As you can read in the first room of the Bonnard exhibition now at Tate Modern, he often took years to finish a painting, putting it to one side before coming back to it and reworking it multiple times. He was known to continue tinkering with his paintings when he came across them hanging on the wall of somebody’s house. At the very end of his life, no longer able to paint, he instructed his nephew to change a section of his final work Almond Tree in Blossom (1947).

Maybe this is wishful thinking, but I find things that have been agonised over to acquire a special kind of depth. In many ways Bonnard is not my kind of painter, but his work rewards close attention. There is hardly an inch of his canvases where you do not find different tones layered over each other – layers not only of paint, but of time and effort – creating a luminous sea of brushstrokes which almost swarms in front of your eyes. And this belaboured quality is all the more intriguing given the transience of his subject matter: gardens bursting with euphoric colour, interiors drenched in vibrant light, domestic scenes that capture the briefest of moments during the day.

Nowhere is this tension more pronounced than in The Bowl of Milk (1919). Pictured is a room with a window overlooking the sea, and two tables ranged with items of crockery and a vase of flowers. In the foreground stands a woman wearing a long gown and holding a bowl, presumably for the cat which approaches in the shadows at her feet. Yet there is something nauseating, almost nightmarish about this image. Everything swims with indeterminacy, vanishing from our grasp. So pallid is the light pouring through the window that at first I assumed it was night outside. The objects and figures crowding the room shimmer as though on the point of dissolving into air. The woman’s face is a vague, eyeless mask. The painting is composed so that if you focus on one particular passage, everything else recedes into a shapeless soup in the periphery of your vision. It is a moment of such vivid intensity that one is forced to realise it has been conjured from the depths of fantasy.

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The woman in The Bowl of Milk is almost certainly Marthe de Méligny, formerly Maria Boursin, Bonnard’s lifelong model and spouse. They met in Paris in 1893, where de Méligny was employed manufacturing artificial flowers for funerals. Some five years later, Bonnard began to exhibit paintings that revealed their intimate domestic life together. These would continue throughout his career, with de Méligny portrayed in various bedrooms, bathrooms and hallways, usually alone, usually nude, and often in front of a mirror.

It was not an uncomplicated relationship: Bonnard is thought to have had affairs, and when the couple eventually married in 1925 de Méligny revealed she had lied about her name and age (she had broken off contact with her family before moving to Paris). They were somewhat isolated. De Méligny is described as having a silent and unnerving presence, and later developed a respiratory disease which forced them to spend periods on the Atlantic coast. Yet Bonnard’s withdrawal from the Parisian art scene, where he had been prominent during his twenties, allowed him to develop his exhaustive, time-leaden painting process, and to forge his own style. The paintings of de Méligny seem to relish the freedom enabled by familiarity and seclusion. One of the gems of the current Tate exhibition are a series of nude photographs that the couple took of one another in their garden in the years 1899-1901. In each of these unmistakeably Edenic pictures, we see a bright-skinned body occupying a patch of sunlight, securely framed by shadowy thickets of grass and leaves.

The female figure in The Bowl of Milk is far from familiar: she is a flicker of memory, a robed phantasm. But like other portrayals of de Méligny, this painting revels in the erotics of space, whereby the proximity and secrecy of the domestic setting are charged with the presence of a human subject – an effect only heightened by our voyeuristic discomfort at gaining access to this private world. There is no nudity, but a disturbing excess of sensual energy in the gleaming white plates, the crimson anemones, the rich shadows and the luxurious stride of the cat. To describe these details as sexual is to lessen their true impact: they are demonic, signalling the capacity of imagination to terrorise us with our own senses.

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In 1912 Bonnard bought a painting by Henri Matisse, The Open Window at Collioure (1905). Matisse would soon emerge as one of the leading figures of modern painting, but the two were also friends, maintaining a lively correspondence over several decades. And one can see what inspired Bonnard to make this purchase: doors and windows appear continually in his own work, allowing interior space to be animated by the vitality of the outside world.

More revealing, though, are the differences we can glean from The Open Window at Collioure. Matisse’s painting, with its flat blocks of garish colour, is straining towards abstraction. As a formal device, the window merely facilitates a jigsaw of squares and rectangles. Such spatial deconstruction and pictorial simplification were intrinsic to the general direction of modernism at this time. This, however, was the direction from which the patient and meticulous Bonnard had partly stepped aside. For he remained under the influence of impressionist painting, which emphasised the subtlety and fluidity of light and colour as a means of capturing the immediacy of sensory experience. Thus, as Juliette Rizzi notes, Bonnard’s use of “framing devices such as doors, mirrors, and horizontal and vertical lines” allow him a compromise of sorts. They do not simplify his paintings so much as provide an angular scaffolding around which he can weave his nebulous imagery.

The window and its slanted rectangles of light are crucial to the strange drama of The Bowl of Milk. Formally, this element occupies the very centre of the composition, holding it in place. But it is also a source of ambiguity. The window is seemingly a portal to another world, flooding the room with uncanny energy. The woman appears stiff, frozen at the edge of a spotlight. It’s as though the scene has been illuminated just briefly – before being buried in darkness again.