Indian Slate Tiles - White clouding / staining

[DerekTimms]

Hi,

We had indian slate tiles laid on top of existing tiles in our bathroom floor Jan 2014.

We then sealed the slated with a FILA intensifier to seal the stone as recommended by the supplier.

Recently white staining has occurred as shown in the attached picture. I have reapplied the intensifier but it comes back.

It is an old property and with the ceramic tiles under I doubt that it could be efflorescence. The adhesive was BAL and recommended by the supplier.

If you know how I can make good or have any ideas what it is that would be appreciated.

Thanks,

Derek

 

[Qwerty]

Damp from under tiles possibly

 

[Lithofin BOB]

As plan tec,Could be salt migrating or bleeding in and up off the grout joint. Or It may be whitening of the impregnator,
I would test strip one stone, if the whitening disappears with the stripper, then it's whitening and an impregnator issue. If not , salt residue- you will need to test a suitable acidic based product to remove this. If you have a spare un laid stone- test this product on this, as not all slates are acidic resistant.
Once you have the test stone clean in the area, work through in small sections and complete the area.
Leave 7-9 days or until fully dry and re impregnate.