Does polishing take a stain out?
Sometimes, and the answer depends entirely on whether the mark is on the stone or in it. Most of what people call a stain is on it. The rest needs a different tool.
Polishing is abrasion. It refines the top layer of the stone with fine diamonds and compounds. It removes anything that lives in that layer, and it cannot reach anything below it. The question is only ever where the mark is.
Three marks that look alike
An etch is a pale, dull or rough patch where an acid has reacted with the polished face of marble, limestone or travertine. It looks like a stain and is not one; the stone has changed at the surface. Polishing, usually after a light hone, removes it completely because the whole problem is in the layer that comes off.
A traffic mark is a path or a patch that has gone grey or dull because fine scratches have broken the reflection. It also lives in the top layer, and it also comes out with honing and polishing.
A true stain is a substance that has gone into the pores: cooking oil, wine, coffee, rust, ink, dye, cosmetics, or moisture that has left a persistent dark patch. It is darker than the stone around it, not lighter. Polishing takes off a very thin surface layer and leaves the discolouration underneath; a higher gloss can even make a stain less noticeable for a while without touching it, and then it is back.
When polishing is the answer
When the bench, vanity or floor has a combination of light marks and surface wear, which is the usual case. A vanity with water rings, cosmetic residue and etching around the basin is deep cleaned, honed and polished as one area, so the finish is even rather than a bright spot where the mark was. A whole-area approach is why a restored benchtop looks like a benchtop and not like a repair.
When it is not
When the mark is in the stone. A deep-set stain is treated before any abrasive touches it, with a poultice: an absorbent paste matched to the contaminant, left on the stone to draw the substance back out. Oil, rust, organic and dye stains each want a different poultice, and one that is safe on granite can damage polished marble, which is why the stone is identified first and why a household experiment can turn one mark into a larger repair.
Some stains do not come out. Very old ones, ones that went in under a coating, mineral discolouration in the stone itself, and some moisture marks are permanent or need a broader plan. Natural stone varies, and the honest goal is a clean, even surface rather than a promise that every mark will vanish. Where a mark will not come out, we say so before the work, not after.
Sealing afterwards
Polishing improves the finish. Sealing slows the next stain. They are separate steps, and both matter. A penetrating sealer goes into the pores and resists water and oil; it does not make the stone stain-proof and it does nothing for etching, so a sealed marble bench still etches under lemon juice. What it gives you is time to wipe up before a spill becomes a stain.
Before you do anything
Blot, do not wipe. Use a neutral stone cleaner and a soft cloth, then dry it. Do not reach for vinegar, bleach, abrasive powder, a scouring pad or a generic bathroom spray; each of those can etch calcium-based stone, strip the sealer or leave residue that complicates the fix. Do not apply a stain remover before you know the stone and the cause. A photo is enough for a first opinion on whether it is an etch, a stain, a coating problem or surface wear, and that is how most of these get quoted.
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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.
I do not know what kind of stone I have. Does that matter?
Not for getting a quote. Send a photo and we can usually tell, and the difference between marble, limestone and travertine changes the method more than the price. If you want to check yourself: marble is usually veined and takes a high polish; limestone is more uniform and often honed; travertine has visible holes; granite is speckled and much harder; engineered stone is uniform with no natural veining and does not etch. A drop of lemon juice on an inconspicuous spot will etch marble and limestone within minutes and do nothing to granite or engineered stone. Wipe it off straight away either way.