You must not let it out of your sight for too long, otherwise you won’t find even the really good pieces untouched. By the way, this does not only apply to Hall of Fame Emscherhalle: there are always leftover cans that are lying around everywhere with which even the most untalented do-nothing can sabotage a master’s work. How to prevent this? Pierce your leftover cans! Without gas one cannot spray and has to pay for the cans first.