gonk31

some tiles now have a waxy coating sprayed on prior to being boxed to prevent scratching that generally needs cleaning off after laying if this is the case then it could be that the silicone is just sticking to the wax and not bonding to the tile, not sure if this is deffo the case but it is a possibility. But i do agree that a decent silicone like the mal micro stuff sill stick better and has great antifungal properties to prevent the all too common black silicone