Used gum is a mid-level aesthetic blight, a kind of acne of the pavements. Worse, for those who have to do so, getting rid of it is a Forth Bridge-type task - no matter how much you clean up, the slowly gurning jaws of the masticating masses will always deposit more. There's a visceral ickiness about used chewing-gum too - it's not quite in the dog-poo league, but there's a lot of alien saliva there. And, unlike most other footpath nasties, gum is a bugger to shift.
Before I started, I thought I'd better read up on what I would be cleaning up. Chewing-gum is made of sugar, flavours, colours and gum base; this last is the indigestible problem. It's usually a synthetic rubber, although it might be a natural latex. As most of the sugar and flavour goes down users' throats, what I'd be cleaning up was effectively pre-chewed rubber.
And so to Stamford Bridge, where I'd be blasting gum off the pavements immediately outside the hallowed ground of London's most loved and hated football team, Chelsea. I meet Barry Wilmot, regional manager of Proventec (maker of gum-busting machines), Jeff Dallison, venue manager for cleaning specialist Cleanevent, and Jon Rees of LVC, which distributes the machines. Jeff tells me that at Stamford Bridge they spend 10 hours a week busting gum: 'It's just keeping it under control, really. You can put up posters and receptacles, but no-one puts it in the bin.' Indeed, the blockwork underfoot is as mottled as a teenager's face.
Introductions over, we get down to the sticky stuff. The process is simple: you take the gum-busting cart, plug it in and wait for it to warm up. You have a nozzle with two buttons: one for steam and one for cleaning solution. Usually, it's a blast of steam, then a few seconds of solution. A wire brush encircling the nozzle lets you mix the cleaning solution into the gum while steaming. The combination soon dissolves the gum into a harmless, non-sticky liquid that disappears down the cracks; any residue is washed away with rainwater. In a few seconds, it's as if the surface has never been sullied.
It would be nice to report that no two splats of gum are identical, but they're all the same. Time on pavement has little bearing on a gum's bustability. Larger splats take more cleaning, but a seasoned operator - typically earning £7.50 an hour - can neutralise a splat every three to five seconds.
One interesting side-effect of busting gum is that the warmth and moisture tend to reactivate the aromas within. As I clean, I become aware of minty whiffs and fruity pongs. 'Are you getting the flavours yet?' asks Brian, laughing. I am. The overall effect is revolting: Juicy Fruit's evil twin, a kind of aromatherapy from hell. And fruity flavours are much worse than mint.
And so it goes on. The machine is impressive: it can run for half an hour on five litres of water, making it both green and clean. This, apparently, is down to the low density of the steam. Kettle steam is dense - as anyone who has burnt a hand in it knows. Gum-busting steam is more rarefied. And to prove it, Rees holds his hand in the steam, and so do I. It feels almost fluffy - with just the faintest whiff of last year's Orbit. It's hard to believe something so mild can liquidate something so resistant.
After 40 minutes, we retire to one of the brasseries around CFC to chew the fat (not the gum). What are the worst venues for gum pollution, I ask? Nightclubs, I'm told, are absolutely awful. People stick the stuff everywhere. But gum-busting is an interior job, too: with a nylon brush replacing the wire one, the machine works on carpets just as well. Rees's most horrible gum-related experience? He'd once had to prepare a thousand gum-splats on paving stones ahead of a trade show demo. He chewed solidly for a week, discovering the true meaning of the pack-back disclaimer: 'Over-consumption may have a laxative effect.'
Coffee break over, we head outside and I do a little more gum-busting; in 15 minutes, I clear a decent patch of the sticky stuff. All in all, I probably bust gum for an hour. Lest MT readers think I was slacking, gum-busting rarely goes on for more than two hours. Continuous use wears out the machine, so operators tend to alternate it with other kinds of cleaning.
On the journey home, I reflect that it's not backbreaking or even particularly dirty work; in a way, it's quite satisfying. But the smell of post-consumer Juicy Fruit stays with you for days afterward, like a tramp's cologne.