Cloudy film on my slate floor seems to get worse when we continue cleaning it
Asked by... Sarah May from Bristol

The Question

I have had someone help me install my new slate floor and it seems to still have a cloudy film on the floor. We have not put the pre sealer on yet, but the more it is cleaned off the more it seems to get cloudy...HELP PLEASE...THANK YOU!!!
 

The Answer

You say you have not sealed the floor yet, so by the sounds of it you could still be wiping off the cutting dust residue on the surface of the slate tiles. We had a similar problem with another customer a while ago who was concerned that he seemed to be cleaning the tiles continually but the dust residue didn't seem to be clearing, this is quite normal with a dusty slate floor.

It is important to change the water in your cleaning bucket every couple of square meters or so to avoid redistributing the cutting, grout residue. This may be a little time consuming but it will be well worth it once the floor is clean and the first seal has been applied. It is worth noting that anything left on the surface of the tile before sealing will be 'SEALED IN' if not fully removed and not disguised by the sealer; as is a common misconception. If in any doubt, ALWAYS DO A TEST AREA in an inconspicuous place.

However, from what you have said above this is just a guess but potentially the problem may be more severe.

I have seen previously on installed Chinese slate tiles (but only black slate) a white bloom appear when the floor is sealed having not been fully dried beforehand. This is known as efflorescence and is caused by the movement of water within the tile itself, as the water passes through the tile it will dissolve the salt content within and leave it as a deposit on the surface of the tile. Some tiles may be more or less affected depending on their porosity or mineral salt content. It is therefore best practice to leave the tiles to dry fully, before sealing.

Should you have an efflourescence problem, you will need to leave the floor to thoroughly dry out for a few weeks. This will enable the floor to breath & hopefully bring all the moisture to the surface where you will be able to wipe off any salt deposits with a dry white cloth or steel wool. In essence is counter productive to use water to try to remove efflorescence as this will just aggravate and prolong the problem.

- asked before 2013
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