Porcelain, stripped back to the tile.
Porcelain does not etch and does not need sealing. When it looks dull the problem is nearly always sitting on top of it: grout haze left from the installation, cleaner and soap film, or a sealer that was applied to a surface that never needed one.
Porcelain is clay fired hot enough to vitrify, which leaves it with almost no porosity. That is the whole point of it and it is also why most porcelain problems are misdiagnosed. A porcelain floor cannot absorb a stain the way marble can, and it does not need to be sealed. Glazed porcelain carries a fired glass layer on the face; through-body and polished porcelain do not, and polished porcelain has fine open pores left by the polishing step that will hold dirt if nothing is done about them.
The usual complaints are a film rather than damage. Grout haze from the day it was laid, never fully washed off, which reads as a permanent cloudiness. Soap and detergent residue in a shower or an entry. A topical sealer somebody applied as a precaution, which is now scratched and peeling in the traffic lane because it was never bonded to anything. Underfoot grit scratches the glaze on a cheaper tile, and a polished porcelain can dull in a lane the same way stone does.
The work is identifying what is on the surface and taking it off without attacking the tile. Haze and mineral film come off with the right acid strength and dwell time; detergent and wax films need an alkaline strip; a failed coating usually needs mechanical help. Then the grout gets its own clean, because the grout is the porous part of the floor and it is normally where the colour has actually gone. What is left afterwards is the finish the manufacturer supplied, which is the honest end point for porcelain.
Where the limit sits: a scratch through a glaze is permanent. Porcelain cannot be honed and re-polished the way a natural stone can, because there is no depth of consistent material to cut into. Anyone who tells you they can polish scratches out of a glazed porcelain floor is describing a coating.
Questions about porcelain tile.
My marble shower looks cloudy. Is it ruined?
Almost certainly not. The cloudy film on a marble shower is soap, shampoo and hard-water mineral build-up sitting on the surface, not damage to the stone. Domestic cleaners either do nothing to it or, if they are acidic, etch the marble underneath while leaving the film in place. A stone-safe strip removes it and the stone underneath is usually fine. The reason it built up is nearly always a failed or missing sealer, so the job finishes with a penetrating sealer that resists the build-up coming back as fast. You will also want a cleaner that is pH-neutral, which we leave with you. Glass doors and tiled walls collect the same film, so a shower that has been cleaned with a supermarket product for years often has both a film on the surface and etching under it. The order of work is the same either way: the film comes off first, then the stone is honed where the acid has dulled it, then it is sealed.
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