Graeme

Hi. I have layed a 50m2 charcoal grey porcelain patio, but in doing so I've got quite a lot of slurry and clement residue over the tiles. I've tried jet washing them but it didn't really make much of a difference. Can anyone recommend a product or a method that will lift this? The tiles look great when wet but as soon as they dry you can see all the slurry/cement sitting on them. Thanks Graeme