Well, I did a trial with a few tiles and then covered them with polyurethane. The trial didn't necessarily go entirely to plan but I was able to establish that PU will be too soft. Epoxy is likely to yellow even indoors, so that leaves me with the following solution: 1. make the tiles thicker (not a big deal) use tile selection and a thicker tile bed to enable a relatively flat surface to be made 3. seal it with a thin polyurethane to protect from mess Thanks for the contributions.

I work as a colourist and the easiest method for a upmarket look is to choose an exact colour to match one of the colours in the tile. I would take the tile to a paint shop and get the colourist it match exactly one of the greys in the tile. Make the depth of the colour a light version. All white walls are on the way out. Lappatto tiles usually have some texture as they are semi polished. This is the latest look in tiles as they give a shine without the maintenance of polished porcelain which had been in. They are usually less slippery than satin or polished tiles depending on the brand.

Looking at the attached photo you can see compared to close to the wall the floor tiles are streaked with white stains. I have tried using vinegar and scrubbing brush and also other cleaning products....

I really like that floor. I hope you are able to keep it once the complexities of waterproofing are revealed. Really large tiles would not be era appropriate. And they were moving away from subway tiles by then. Perhaps 20-25cm square in running bond for that decade? Colour will be easier to pick when the green is gone. I think bright whites could be useful accents but were not really available back then, except whitewash. So depends on how true to the age you want to be or if you’d prefer to have your own blend of the best of two eras.