Cleaning is satisfying. There's just nothing better than restoring something that has been neglected back to its former glory; and the dirtier it was, the better it feels.
And what gets grimier than the things that get left outside? Faced to deal with the elements - the rain, the mud, the smog and pollution of our filthy world, these objects seemed beyond rescue, doomed to decay in a fetid morass of crud and muck.