What should we do to remove the white deposit

Dear Sirs,

 

I have been struggling to find the solution to a problem that I have with a slate floor.  I have asked a number of 'experts' with little success.  Having visited your website, I have paid the 5$ fee through PayPal (ref 42S 5360 7523 5528 41 dated  06/11/2004) and would ask you to submit my 'question' to your panel of experts.

 

So, here is an outline of the problem:

 

In Granada, Spain, we have restored an old Moorish house and have laid a green slate floor.

 

>  the floor is Spanish green slate tiles that are about 400 mm square and 15 mm thick(smooth on the 'down' side and natural surface on the exposed side)

 

> the flooring was laid on a concrete base in June last year and after completion looked great (i.e. green)

 

> our cleaner regularly mops the floor with water to get rid of the dust (ever present in this part of Spain!)

 

>  within a few months, the floor developed a white deposit.  Initially, we scrubbed the floor and this removed what appeared to be like very fine silvery 'silt'.  The 'silt' settles to the bottom of the cleaning bucket and feels like a slippery clay-type substance.

 

>  however, the floor never really cleaned up and has returned once again to pale greenish white.

 

>  A shelf that was covered in the same slate has remained green whilst the floor has the white deposit.

 

>  The deposit appears bonded to the surface and is almost iridescent or silvery in the light. It is not fluffy like efflorescence, but appears natural. If you wipe it with a dry cloth or finger, the white comes off like dust.  If the floor is wet, the green comes through to some degree but returns to white on drying.  Scrubbing with a brush can remove the majority of the white deposit but it reappears in time after our cleaners mop the floor. Even after scrubbing, the tiles dry 'white'.The deposit is not soluble in water.

 

>  Apart from spoiling the look of the floor, the white powdery dust marks anything that is placed on the floor.

 

The composite photo shows the floor (right) originally and (left) now.  The photo on bottom right is the shelf.  The photo on the bottom left shows a tile that is unaffected with the adjacent ones affected.

 

So, our question is:

 

What should we do to remove the white deposit and what action should be taken to stop it happening in the future?  If we should use specialist treatments, could we be directed to a supplier who either has an outlet in Spain or in the UK?

 

We look forward to your suggestions and assistance.

 

Best regards,

 

John

 

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