Thanks Joe. All the research I'd done seemed to indicate pressure, at least 1000 psi, to be a prime factor. I haven't tried the machine out as I haven't got a hard floor wand. Any suggestions? I've been looking at a couple of Prochem ones but there's also a 300mm two jet wand from Restormate for £134.00. Is it a case of 'you get what you pay for'?