White residue on porcelain (slate finish)

[icctiling]

Hi all
finished laying 600x300 porcelain (slate finish) and grouted, in my sisters bathroom.
went to check them about 2-3 days later and found a white chalky residue on tiles.
very random, i.e. Some on centre of tile, some close to grout lines.

have added some photos to show

checked the remaining tiles out in shed and a light speckle of white residue is on unused tiles.

initially thought some effervescence and have treated with tile cleaner but still some remaining.

when tiles are wet the residue disappears.........would anyone recommend treating with some form of oil (baby oil??) to bring up the slate finish and erase the white residue ???

just asking if anyone has come across this, and how can I treat?
Any advice would be great

thanks in advance

 

[Dave]

It could be polymer or cement residue from the grout , try some lithofin cement residue remover first , should do the trick , use a diluted mixture first on an inconspicuous area , towel dry and see results .. Use a stronger dilution if not removing .. Wear appropriate PPE...

 

[swanman]

good advise

 

[Lithofin BOB]

You state the same contamination / lighter is on the unlaid tiles, this may be a whitening to a possible transit wax, or manufactures coating . test the cem res remover as suggested by david or if your tile cleaner is acidic based - re clean, contact your supplier , they can often tell you if there is a coating that may need to be removed or if they have had this before.

if this was a transit or polymer based issue you wil need an alkali based cleaner not acidic to poss break this down.

 

[Spud]

the tiles could be scuffed , have damaged surfaces , how were they packaged /transported ?