Terra Cotta clay pavers, That had a coating real dirty. @Mikey P said hit it with a nuetral cleaner and light scrub, low psi rinse. Well I declined it at first, but she called and said please. So I hit it with slop and gobble but added last step to lower the ph! White brushes crb and 300 psi with a gecko tile wand! It cleaned up real nice the lady was happy!