Cleaning grout stains of unglazed ceramic tiles

dirty_magic

We had the same problem, I was worried it would never come off! White vinegar mixed with water and a plastic scrubbing sponge worked perfectly!

cyclonebri1

First of all it's not staining, it's the micro pores, not the porous surface, that have filled with grout and therefore those areas appear grey or faded.
How to fix?, It's his problem not yours yet. If he is really a tiler he will have come across this before and will know the remedy, I'm thinking mortar cleaner but would not recommend unless I'd cacked up myself.

If he wont come back threaten trading standards

JEN22

Use Lithofin cleanersyou will find them on Amazon. Superb. But they don't require sealing