QUESTIONI have just had my bathroom renovated and once the tiling was done with a matt finish porcelain tile (light of colour) I was left with streaks and drips that where very noticeable when the light hit them at night. I repeatedly asked the supplier to clean the walls after the job and they took about 2 weeks to address this.
When they did eventually turn up to clean them they realized the job was quite hard. They had used an epoxy grout and every chemical (used many and even sanded the tile - as I cam hime to a light dust in the bathroom) they used did not get these stains off them. The stains however did dull down and are now only visible when the bathroom has condensation on the walls. They have told me this was not an installation error but is a tile error. I don't know who my complaint should be with, the tile manufacturer or the installer. Could you help with what you think the most likely cause would be. Thank you so much in advance
ANSWERANSWER - I am guessing that you had a through-body/unglazed porcelain tile since you said it was a matte finished porcelain tile and you said that the installers were able to grind the surface to try to remove the stains.
Because you said that the tile had streaks and drip-like stains, it is possible that the installer used a corrosive acid, like muriatic acid, to clean the cement film off of the tile after they installed it, and the acid etched the the tile surface. If drips of an acid solution is left on the tile without rinsing right away it is possible it etched the surface. Etching is where the tile surface is chemically transformed and can't be cleaned.
On the other hand, there is a condition called Optical Haze that can occur on polished through body tiles. This is where the manufacturer did not properly polish the tile and you see a blotchy or streak-like condition on the tile when you look under certain direct lighting conditions. It can not be removed without re-polishing the tile. If your tile has a slight hone finish to it maybe that could be it.
If you have extra tile left over, which we call attic stock, take some of those pieces and look at them under various lighting conditions. If you see the same types of drips and streaks, then that would suggest it was a manufacturing problem. If the tiles don't have those conditions, then it would suggest the installer or someone else caused the condition.