There is a marble and slate cleaner out there by PLASPLUGS. Its around 20 euro a litre and available in woodies and the like. It works on slate and marble. Can I ask what sealer you used?
There is a marble and slate cleaner out there by PLASPLUGS. Its around 20 euro a litre and available in woodies and the like. It works on slate and marble. Can I ask what sealer you used?