porcelain tiles showing some mottled marks after cleaning?

[AliGage]

Through bodied porcelain is the same colour from face to back but porcelain bodied tiles with applied finish are not ...

Exactly. Anyone thats ever chipped the cut on a tile running it through the wetsaw would recognise it. Some tiles that aren't full bodied (don't know if that's the correct term but a porcelain tile that pattern and colour runs the same throughout is what i call "full bodied") have a white undercoat under the coloured finish layer on the tile. I think what's happened here is the cleaner has "thinned" the top layer and the lighter marks are the "undercoat" showing through what's left of the finish coat.

I hope that all makes sense. If i can re-create the "chip" at work this week i'll take a picture and post it.

 

[xelaris]

Exactly. Anyone thats ever chipped the cut on a tile running it through the wetsaw would recognise it. Some tiles that aren't full bodied (don't know if that's the correct term but a porcelain tile that pattern and colour runs the same throughout is what i call "full bodied") have a white undercoat under the coloured finish layer on the tile. I think what's happened here is the cleaner has "thinned" the top layer and the lighter marks are the "undercoat" showing through what's left of the finish coat.

I hope that all makes sense. If i can re-create the "chip" at work this week i'll take a picture and post it.

Maybe you are right...this Porcelanosa model (Graphic Nature) is full bodied porcelain but the top looks slightly darker (quite noticeable if viewed from the "thickness" side). In fairness, the texture doesn't seem to have been affected - no scratches as such - but maybe the "finishing" has been partially washed or weakened by the cleaning.

btw: I've tried to clean a spare tile (same model) with Swarfega and also some other cleaners and I can't reproduce the same damage...

 

[xelaris]

Update:
I bought another box from the Porcelanosa showroom in Manchester (not any Ebay seller)....all the new tiles present this "defective" mottled/spotty pattern - maybe this is how these tiles were designed?....it might just be a question of taste?! If so, why the Ebay seller tried to cover up the original "design"?
Anyone keen on these mottled theme? Not me, nor someone I know who went to scrub the tiles thinking it was some wax residue....
There is no definite conclusion to this mystery....either the design is a bit of a hit and miss (more of a miss in my opinion)...or at Porcelanosa someone decided to smuggle some defective batches here in Manchester.