I am trying something that should be trivial, without success.
I've done a search and found a similar question, but I don't want to change the shader, I want to keep it simple and I think that what I want to achieve should be reachable with the simple PRINCIPLED BSDF node.
Yet, for some reason I can't make it work.
I have tried raising the specular factor, it had nearly no effect. I still don't understand what that parameter does, as I would expect an increase in... specularity factor. It doesn't happen.
I tried to play between metallic and specular, but of course this completely changes the way the tiles look.
I just want to increase the amount of reflectivity of the tiles, so that the WC and bidet and the sink will reflect a bit on the tiles.