They're only a few years old and I suppose it serves me right for getting what I thought was a 'bargain'!! they are in the hallway and are porous and now have ingrained dirt even though this floor is mopped regularly. I've tried absolutely everything including white vinegar. I need something to penetrate and lift it out but nothing seems work. Help.
According to my 'trade secrets' book, sour milk will bring your floor up a treat. Also natural floor tiles should be washed with COLD water not hot. Don't know if it works but hey, nothing ventured and all that.