I have laid some natural slate tiles as a hearth. They were bedded on
standard mortar and grouted normally. I then treated them with HG porous
The problem is most of them have now exuded some white powder which
smells salty. It also is ompossible to get rid of. I scrub and wash it
off but it just returns. HELP PLEASE !
My hearth looks awful, anyone know what to do.