Dirt: The Filthy Reality of Everyday Life – review
Wellcome Collection, London

By Laura Cumming

Dirt, the Wellcome Collection's riveting new show, opens with a shocker: a window so filthy not an inch of glass is visible beneath the grime, a thick brown substance that twinkles repulsively in the gallery lights. It is gutter dirt, pavement dirt, the dirt of cities blown with dust and litter. It causes immediate recoil.

And it covers the sill and frame, this unspeakable stuff, so that the whole thing becomes a solid block of dirt. You cannot see through the glass (if you can bear to look) its transparency stopped, its vision blocked. This window is effectively blind.

It would be hard to overstate the physical effect of James Croak's 1991 sculpture, which is literally cast from street-sweeper's dirt. No matter how much art history it condenses – figurative yet abstract, with its resemblance to American minimalist sculpture; realist yet conceptual with its wink at Duchamp's Large Glass – it's the primitive impact that counts.

Does it smell? Is it shedding filth? Asbestos? Germs? You stand away. Dirt is everywhere, and we do not wish to confront it.

Anyone prepared to overcome this natural aversion, however, will be enthralled and enlightened by the Wellcome show. It has more than 200 exhibits, from paintings, films and sculptures to Antonie van Leeuwenhoek's amazing 17th-century microscopes and Joseph Lister's earliest sterilising inventions, from hilarious soap ads and quaint portraits of Victorian mudlarks and Inspectors of Nuisance to dark exhibits from the Dresden Hygiene Museum: dirt as devastating racial metaphor.

The curators rake the murky world of dirt very thoroughly, and dramatically, pondering the associations with cleanliness, godliness and social order – "Arrest All Dirt!" exhorts the 1920s London Bobby, scouring what looks remarkably like Westminster with his torch – as well as religion, ethics, class and mortality. "You & I are Earth", declares the script on a Delft plate over which someone has taken exquisite, if poignantly futile, care.

What binds it all together is a central theme. The show is very purely about seeing, appearances, visibility. We think something is dirty because it looks dirty (though what about soil, for instance, source of so much sustenance?). But then again, a century of relentless advertising has persuaded us that dirt is invisible too – just because something looks clean doesn't mean that it is.

Dirt is grey, brown, something mouse-coloured between the two. It seems to have a base colour in some people's minds. But of course we cannot see most of it (the world's worst and least polluted air appear identical in Angela Palmer's installation of glass vials), and if we could then it might alter some preconceptions.

Dust mites, for examples, turn out to be a beautiful mother-of-pearl pink. Algae can be green, cobalt, turquoise. Beneath Leeuwenhoek's microscope, he could see the plaque scraped from his own teeth dancing like fireflies. (You can see what he saw too, enlarged on a plasma screen).

For every Victorian painting of The Great Dust Heap at Kings Cross, or its modern equivalent, video of teeming developing-world landfills, there is a focus on detection, on bringing the invisible to light. Indeed the show's central work is surely John Snow's map of Soho during the cholera outbreak that devastated the area around Broad Street in 1854.

Snow was obsessed with discovering the source of the plague, at this point still believed to be miasmic. He walked every street, knocked on every door, interviewed every survivor he could find. The dead are recorded as black rectangles on his map, eerily like coffins or dominos, stacking up corpse by corpse, house by house. From the visual patterns Snow was able to deduce his momentous conclusion – that the Broad Street water pump must be the source of the infection. Without this map, black and white and utterly unforgettable, the understanding of cholera would have been held back. It is masterpiece of information expressed through design.

Of course it is easier to look at a map than a flask full of human fluids infected with cholera. I cannot pretend that there are no moments of revulsion in Dirt. The vast installations of tomb-like slabs made of human faeces by the artist Santiago Sierra, the horrifying photographs of Victorian slums in Glasgow, clogged with filth in which infants sit.

Some of the exhibits are actually frightening. The primitive "epidemic ambulance", a heavy black trunk on wheels, halfway between pram and coffin, life and death, with a tiny window for the entombed victim to look out, is the embodiment of dread. It pierces the imagination more effectively than many a work of art.

There is a long tradition of dirt in art – Richard Long's mud paintings, Piero Manzoni's canned excrement, Joseph Beuys's sweepings from Karl-Marx-Platz. It wouldn't be hard to come up with a filthier selection than this one, which is somewhat fastidious with its jewelled brooms and Persian carpets created entirely out of the dust you might sweep under said carpet. But this is just the contemporary art.

And given that most dirt is either ugly or invisible it is no small thing that the curators have managed to materialise its presence, its effects, so strongly. Who could forget the 1831 engraving of a young Venetian woman before and after contracting cholera, from health to agony in a matter of hours, the characteristic hue of the skin most potently imitated and conveyed by the blue tinting of the print.

Or the dire sight of William Macewen's 19th-century watercolour of a gangrenous foot, itself affected by something like the very condition it portrays. You can make the comparison with period photographs of this very disease in a nearby room. This is what makes the Wellcome Collection shows so unique: they make no separation, physical or moral, between art and life.

A great art show can alter your way of looking. You leave the building and see the streets peopled by Degas or the landscape through Monet's eyes. Something like this may happen after Dirt, as one notices every particle of grime and every noxious fume in Euston Road outside the Collection.

But even while you are in the show something changes. The focus is thrown, the emphasis shifts. Staring at Pieter de Hooch's beautiful painting of a woman sweeping a room, so that the light appears to polish the floor, you become mindful of the brown dirt that has accumulated on the canvas itself – opposing her labour, and his vision, by turning the bright room dim and dirty.

And Bruce Nauman's film of hands vigorously washing themselves has always irked me as a spectacle of obsessive-compulsive disorder, obsessively repeated. But it is not so simple. What I have never noticed before is the enemy below: the disgusting filth of Nauman's sink.