Sealers, enhancers and coatings: which is which.

Protection is not repair. A scratched, etched or stained surface is corrected first, because whatever goes on afterwards preserves what is under it. With that settled, the choice is between three families.

Penetrating sealers

Also called impregnators. They soak into the pores and line them from inside, slowing water and oil getting in while leaving the look, the feel and the breathability of the stone unchanged. Nothing sits on the surface to scratch, peel or haze. This is the right product for a marble bench, a limestone floor, a travertine bathroom, terrazzo, sandstone and grout, and the only one that belongs on a food-preparation surface. Better formulations repel oil as well as water. What none of them do is stop etching, because the acid reacts with the face of the stone above where the sealer sits.

Enhancing sealers

A penetrating sealer with a colour effect: it darkens and deepens the stone the way water does, and stays that way. On slate, some travertine, tumbled pavers and external feature stone that can be exactly the look wanted. On a pale honed marble floor or a cream limestone bathroom it is a permanent change of appearance, and it also darkens every repair and natural variation so that future spot work is harder to blend. It is tested on a hidden area first, always, and used on purpose or not at all.

Topical coatings

These sit on top as a film: a wet look, a gloss, a sacrificial layer. There are commercial floors where a coating system is the right call for maintenance. On natural stone in a home they are mostly the cause of the problems we are called to: applied heavily they dry cloudy; over time they yellow, trap moisture in a bathroom, hold dirt at the edges of the traffic lanes, peel, and can be slippery. Removing them takes a controlled strip, and the strippers that shift a coating can etch the stone under it. A floor that is glossy in some places and cloudy in others usually has one.

Why the wrong one shows fast

Applied over dirt or moisture, any of the three blotches. Over-applied, a penetrating sealer leaves a residue haze; a coating leaves a plastic one. An enhancer on the wrong stone makes a light floor look permanently damp. And none of them fix what was under them, which is why the first sign of a wrong choice is a dull patch that was already there and now cannot be treated without removing the product first.

Choosing

By stone, finish, room and use, not by shelf. A kitchen island wants oil resistance without a film. A shower wants absorption slowed without slip. An entry floor wants durability and easy cleaning. A patio might genuinely want an enhancer. Ask what the product will and will not do and how the surface is to be cleaned afterwards; if the answer is vague, the result will be.