Had a job a month or so ago where customer spilt hair dye onto polished porcelain tiles - long story short of having Kev Martin on speed dial all day we ended up applying a poultice to all the areas. Left for 3 days, 90% removed, some of the larger stains had very faint stains still there.
Was doing some other work for the guy so agreed to put another application down while we worked no problem.
Returned 2 weeks later to finish the other job and re apply - all the stains had gone....
Could it be that the faint stains still visible had been brought to the very top of the surface and the normal cleaners mop etc would of removed it?
Could some of the chemistry stayed in the tile and disintegrated it at all?
Not a bad problem at all but be interested to know the reason why!