Cleaning limestone without harming it.
Limestone looks expensive one day and patchy the next if it is cleaned like ceramic tile. It is a delicate natural stone and it is cleaned like one.
Limestone is calcium carbonate: acid etches it on contact, water and oil go into it readily, and its usual honed finish shows residue and moisture more than a polished one would. Every cleaning decision follows from that.
The routine
Dust first. A soft dry mop, a microfibre pad or a hard-floor vacuum, because grit under a wet mop is sandpaper. Then warm water with a pH-neutral stone cleaner at the stated dilution, applied with a damp mop, not a wet one; limestone is porous and excess water goes into the stone and the grout and discolours both. Work in sections and change the water when it clouds, or you are spreading residue around. Dry with a soft cloth or a dry microfibre mop, which stops water marks and evens the finish, and matters most on honed stone.
The products
A dedicated stone-safe, pH-neutral cleaner, used sparingly: over-dosed cleaner leaves a film that dulls the floor and holds dirt. Never anything advertising degreasing, mould removal, limescale removal, bleach or citrus unless it states it is safe for natural stone, and mostly not even then. Vinegar, lemon, descalers, bleach and abrasive powders create damage on limestone almost immediately, not gradually. No rough pads, no stiff brushes.
Spills and marks
Blot, do not wipe; wiping spreads the liquid across the tile and into the joints. Follow with the neutral cleaner. A mark that has already set has usually gone into the stone, and attacking it with something stronger from the cupboard removes the finish rather than the stain. That is a poultice or a professional clean. Dark grout, embedded soil and traffic lanes that neutral cleaning no longer lifts are a sign the floor wants mechanical cleaning, honing or resealing rather than more mopping.
What a clean floor should look like
Honed limestone should be smooth and matte; polished should be clear. Neither should feel sticky, gritty or uneven afterwards, and neither should look stripped or chalky. If it does, one of two things has happened: the wrong chemical, or a film built up from repeated cleaning. If the surface has lost clarity, feels rough in patches, or has cloudy marks that do not wash out, cleaning has stopped being the answer and restoration has started: embedded contamination removed, etching honed out, the surface refined, and a sealer applied so it is easier to keep.
Steam
It sounds like a shortcut. Heat and moisture stress the stone, affect fillers and sealers and push contaminants deeper into porous material. On a limestone floor of any value, ask before using it.
Sealing
A penetrating sealer slows absorption and makes routine cleaning work better, because dirt stays near the surface. It does not stop etching, and a sealed floor still dulls under a harsh product. Reseal when a few drops of water darken the stone rather than bead, sooner in entries, kitchens and bathrooms than in a quiet hallway.
The habits are small: mats at doors, spills early, gentle consistent mopping, felt under furniture, and the stone-safe bottle kept apart from the general cleaners so nobody in a busy house or a cleaning crew reaches for the wrong one.
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Related questions.
Can etched marble be restored, or does it need replacing?
Etched marble can be restored in place, and replacement is almost never the right answer. Etching is a thin layer of the polished surface dissolved by acid. It is not a stain and it does not go deep. The mark is honed off with diamond abrasives and the area is re-polished to match the rest of the top. On a benchtop that is usually a couple of hours of work, done on the bench with the kitchen protected. Deep etching that has left a visible dip takes more honing and blends less perfectly, and that is exactly the sort of case we cut a test patch for before committing. Replacing a benchtop means a new slab, templating, fabrication, removal, plumbing and a splashback, and weeks without a kitchen. Restoring it is a fraction of that.
How often should marble be sealed?
It depends on the surface and what it takes. A kitchen benchtop or a shower, which see acid, oil and water daily, are usually resealed every twelve months. A floor or a table in a lower-traffic room goes two years or more. The honest test is the water bead: a few drops left on the stone for ten minutes should sit up. If they soak in and darken the stone, the sealer has worn and it is time. We add every surface we seal to a reminder list and message you when yours is due, so you do not have to remember. A sealer is not a coating sitting on top. A penetrating sealer soaks into the stone and slows how fast liquids get in, which buys time to wipe a spill before it becomes a stain. It does not stop etching, because acid attacks the surface of the marble itself rather than soaking into it, and nothing short of changing the stone prevents that.