That's from Motley Crues autobiography, titled 'The Dirt'. It's a no-holds barred chronicle of the bands decent from debauchery, addiction, near death to further debauchery and snorting ants off the pavement with Ozzy Osbourne. What the Crue mean by 'The Dirt' isn't just their patio trash. They mean the whole unexpurgated story.

In rock and roll, dirt equates to authenticity. Being dirty means being real. Sometimes it can symbolise very particular positions. Hippie dirt was about being natural, Punks filth was an eloquent statement of opposition to the establishment: The Clash dirty like freedom fighters, the Sex Pistols filthy as Dickensian urchins. But being revolutionary didn't always mean being dirty.

For early Modernist architects, dirt meant the squalor of the recently industrialised city: slums, disease, poverty. Architects and planners wanted to erase these old cities, filthy with history, and build clean environments fit for what they described as the 'industrial artisan'.

If look you back across the landscape of history, the view helps explain why Modernist architecture looked like it did. Those beautiful white Modernist villas of the 1920s and '30s are set against a backdrop of belching dark clouds of late nineteenth-century pollution - the kinds of urban scenes described by Marx and Dickens. The London smog became personified in fiction as a thick fog that shrouded evil. It sometimes assumed solid form as a criminal, murderer or mythical half-man, half-beast.

Modernist architecture used rational logic and science to combat ignorance, dust and disease, just like Sherlock Holmes' scientific proto-forensic techniques against Victorian urban sin. Cleanliness was central to the Modernist project. Its ambition was clean Euclidian space, manufactured by industrial processes. Cleanliness meant honesty and authenticity. Cleanliness was utopian. It was political in the eyes of Le Corbusier, who warned that cities were so terrible that there was a stark choice: 'architecture or revolution'. Cleanliness was aesthetically resolved by Mies van der Rohe in projects like the Barcelona pavilion, where chrome columns reflect polished marble through large sheets of glazing.

You can still see the nineteenth-century filth that turned London black, but you have to look harder each year. Those once sooty buildings are gradually being cleaned. St Pauls is the latest. It is halfway through a 40 million pound restoration project to mark its 300th anniversary in 2008. The West Front - the main entrance facing the top of Ludgate Hill - has recently been unveiled. This part of the project cost five million of the late Sir Paul Gettys pounds. The work comprised mainly stone cleaning and repair, but also included the re-carving of eroded stones, re-gilding, repairs to the clock face and bells and the relaying of the west steps. Lady Getty says: 'Paul remembered St Pauls from a boyhood visit to London with its West Front looming in the fog above Ludgate Hill. He loved the Great Northern Baroque Cathedral of his Patron Saint and would be overjoyed to see it shining and clean again.' Like many of Londons other significant institutions, it is built from white Portland stone. The change of colour, before and after restoration, is high-contrast dramatic; the transformation from black to white is as startling as Michael Jacksons and almost as strange.

Gleaming white and gold, St Pauls looks odd, as though newly born or a heavenly apparition. In some ways a layer of meaning has been removed from the building: the dirt and filth had built up over the centuries, reflecting the life of the city around it. In its most famous photograph, St Pauls is solid amongst the billowing smoke and flames of the Blitz, symbolic of Londons finest hour. And the dirt in and on St Pauls itself assumed significance when Cornelia Parker collected dust from the Whispering Gallery, forming it into ear plugs. Perhaps she was suggesting that we are deaf to historys whisper.

Conservation is assumed to be benign and essentially neutral, but actually, cleaning is a highly charged act. Restoration is like rewinding history, and as anyone who has seen the Back to the Future films, this can get complicated. The process of cleaning idealises the object and, just as there are different kinds of dirt, there are many varieties of cleanliness: scrubbed up and plain like the front step of a house, or polished by minimum-wage guest workers into a state that feels unreal by machines pushed.

The Grey Blanket is a project by graphic designers A Practice for Everyday Life. The phrase refers to the layer of filth that coats London and their intervention was to rub out pollution build-up to create four metre-long typographic messages. It is a kind of anti-graffiti, inscribed by taking away rather than adding. The messages are ephemeral, existing as Emma Thomas puts it, until 'the city is completely cleaned up, or enough pollutants build up again for the message to vanish'. The project suggests that cleaning could be used in imaginative ways to create temporary interventions in the fabric of the city. Imagine cleaning new patterns across the face of St Pauls. Like the finger that traces text into the grimy canvass of a white van: 'I wish my wife was this dirty'.

Anthropologist Mary Douglas studied dirt and its cultural significance in Purity and Danger: An Analysis of the Concepts of Pollution and Taboo (1966) Douglas cross-culturally examined definitions of impurity and argued that pollutants play an important role in maintaining social structures. She defined dirt as 'matter out of place', suggesting that dirt is culturally constructed rather than a naturally occurring phenomenon. Dirt is more than mess. It is as alive with culture and meaning as bacteria.

Dirt is also an intrinsically architectural material. Both architecture and grime are by-products of the grinding wheels of civilisation. Architectures unnatural and artificial environments help define what dirt is. Look under your sink at those products designed to help keep your house clean if you need evidence: Cillit Bang!, Cif, Mr Muscle, polish, bleaches, peroxides, detergents. Think of the time, money and physical effort spent cleaning architecture. Think of contract cleaners polishing the marble foyer of a Wall Street bank after-hours. Think of crumbs falling from a croissant and being trodden into a carpet. Imagine the action of a vacuum that disturbs the carpet fibres, dislodging the crumb while the force of the vacuum drags it upwards into a stainless steel tube. Think of the constant leaking, flaking, staining, smearing, shedding, spilling of everyday life. Think of the action of detergent - imagine it dissolving dirt like an animation in a washing powder commercial. Think of an abrasive scouring action in concentric circles.

Sometimes, architects take an alternative approach, where dirt and architecture enjoy a more positive and constructive relationship. Caruso St Johns recent entry for the Londons Architecture Foundation competition recalls the streaky facades of London buildings. They liken the polluted surfaces 'to the effect of mascara and blush in beauty treatment'. They propose 'a building of pure white concrete with a surface of fine grooves and polished aggregates. Over time, the rougher surfaces will gather dirt and darken, highlighting the brilliant smoother surfaces, and revealing the figures of huge typography, spelling out the letters AF, interwoven into the facade. The patina of history would make a thoroughly contemporary super-graphic on the building's elevation'. Adam Caruso adds 'I suppose that it has something to do with being provocative. Perspectives of mainstream architecture always show thousands of people, purposefully milling about the new project, looking into the Books etc. window and drinking Costa coffee. The building and the people are always very clean. Good cities are not shiny and new like this, places like Rome and London can tolerate a lot of dirt, emptiness and pathos, and good architecture should not rely on 'newness' to be valid.'

I'd heard that Adam had been in a punk band with artist Mark Pimlott. So I asked if this dirt was a kind of punk filth creeping into his work: 'Our band played some Jam and Who covers, two famously 'sharp' bands, so the dirt has nothing to do with punk.' While the Jam might have been suit sporting mod revivialists, they also wrote Mr Clean , to whom Paul Weller sang 'if i get the chance i'll fuck up your life'. Like different kinds of dirt, there are different kinds of clean too.

French firm R&Sie are working on a project for an art gallery in Bangkok called B-mu. Their response was not to the local building vernacular or the massing of the neighbourhood, but to the dusty atmosphere of the city: 'Bangkok is a very dusty and luminous city. The pollution cloud, CO2 residue, filters and standardises the light with only grey spectral qualities.' The building itself is a jumbled stack of boxes - white cubes arranged as a kind of 3-D labyrinth. An aluminium lattice is draped over this with an electrostatic charge running through it. The static attracts and holds dust, which gradually forms the exterior of the building. It would be filthy on the outside, clean as a cosmetics counter on the inside, as though a Victorian dust-yard has enveloped a space station. It's a juxtaposition of states as striking as baked Alaska, dramatising and exaggerating the difference between interior and exterior: the exterior skin as an interface with the outside world and the interior as an artificial world. Francois Roche describes it as 'schizophrenic' and the exterior as 'plunged into the an intoxicating urban chaos' - like shifting sands of a desert, in a state of flux over the solid lumps of the city. The project is a kind of perverse high-tech, hijacking technological innovation to achieve a disturbing end. Most high-tech architecture uses machinery to the point of fetishism in order to deliver a well-tempered environment (beautiful air-conditioning ducts, exquisitely detailed window cleaners hoist and so on). The B-mu looks like it will offer an experience similar to the last hours of Pompeii, delivered with a detached coolness.

Dirt is a symptom of the passing of time over an object. Its use as an active design element is shows an acceptance of the real context of architecture, which is place and time. Idealised versions of architecture are often seductive precisely because they brush the mess of everyday reality under the carpet. Dirty architecture suggests high concept buildings with their feet in the gutter.

R&Sie
APFEL
Caruso St John
first published in contemporary