Guides · Maintenance

A bathroom stone top marks before a kitchen one

In short. In a bathroom, stone is not worn down by what gets spilled on it: it is worn down by what it is cleaned with. Limescale is calcium carbonate and marble is calcium carbonate, and a limescale remover cannot tell the deposit from the stone carrying it. That is where a vicious circle begins which does not exist in a kitchen, and it is recognised by one sign: the ring that keeps coming back in the same place.

In a kitchen the acid arrives by accident; in a bathroom it is sprayed on

In a kitchen the acids that reach the stone are foods: lemon, vinegar, wine, tomato. They arrive by chance, they are seen, and the worktop gets wiped dry after cooking anyway. They are episodes, and between one and the next the surface stays dry.

In a bathroom the acid does not arrive by accident: it is chosen, bought and sprayed. It is a product, used exactly where limescale forms — the band of top around the basin — and left to work, because the instructions say to leave it to work. Then the gesture repeats every week, on a band nobody dries and which is wetted several times a day. The difference between the two rooms is not how delicate the stone is: in one the acid is an accident, in the other a habit.

Limescale and marble are the same substance

The limescale that builds up around a basin is calcium carbonate left behind by evaporating water. Marble is a rock made of calcium carbonate. A limescale remover works because it contains an acid that dissolves calcium carbonate: that is its operating principle, not a side effect. On the top there is no chemical boundary between the deposit and the stone carrying it, and the product has no way of stopping at the first.

Two data sheets of products on the market are enough. A domestic sanitising limescale remover, declared by its own maker for tiles, basins, taps, shower enclosures and baths, contains sulfamic acid and formic acid. A professional descaler for sanitary ware declares hydrochloric acid in the 5-15% band and a pH below 2. Neither sheet carries a single warning about marble or natural stone: not because they are compatible, but because nobody wrote them with a stone top in mind.

The information, though, is owed. The European detergents regulation requires the packaging of products sold to the public to state the content in percentage weight bands, and the manufacturer to make an ingredient data sheet available on a website; for professional products the same information sits in the technical or safety data sheet. The name of the acid can always be found: it has to be looked up before buying, not after the damage.

The vicious circle, which is the thing nobody writes down

Damage in a bathroom is not a single accident: it is a progression, and each step sets up the next.

• hard water leaves a white deposit on the band around the basin;
• the deposit shows, so the product that removes it gets picked up;
• the acid dissolves the deposit and, with it, a film of stone: the surface loses its gloss and turns microscopically rough;
• a rough surface holds water and dries more slowly than a polished one — and how much water a stone absorbs is a measured property, with its own test method, EN 13755;
• so the limescale comes back sooner, and in the same place;
• and the circle restarts from stone that is already worse than before.

That is why the ring around a basin “will not come off any more”: it has not become permanent, only what is being looked at is no longer a deposit to remove but an area of etched stone that holds it. Water on its own does not attack marble, because calcium carbonate fears acids and not damp: what it does is keep the stone available to whatever lands on it. The sign to read is repetition: a mark that returns in the same place, and ever faster, is not dirt, it is a surface that has changed. How a dull patch is told apart from a stain is in the guide to stains and etching.

On light and dark stone the same damage reads the other way round

On a dark polished top limescale is white and shows at once, while etching appears as a grey, lifeless area which looks like dirt and prompts a stronger product. On a light top the opposite happens: limescale is almost invisible and etching shows only in raking light. On light tops the damage walks on for months unnoticed; on dark tops it is noticed early and treated with the wrong thing. Before deciding that a top is dirty, look along it: etching changes the way light is reflected, dirt does not.

A bathroom holds liquids a kitchen never sees

A bathroom top carries a pharmacy on its back: toothpaste, perfumes and alcohol-based products, nail polish remover, hair dye, cosmetics formulated acidic, medicines, contact lens solutions. They sit in bottles that drip at the neck and stay there, and they share one dangerous trait: they look like water, and a colourless drop left to dry gives no signal until the day it is seen against the light.

For these, a list of forbidden products is useless, because they change constantly: what works is a rule about place. Whatever is not known does not get set down on the stone, and a tray costs less than re-polishing.

The finish does not change the chemistry; it changes what is seen

A polished finish reports etching at the first contact, because gloss is the first value to be lost. A honed one hides it for longer, but holds more and needs cleaning more often. The difference is not resistance — the acid works the same way on both — but legibility: in a bathroom, where the episodes are many and small, a surface that does not photograph every contact is usually the more sensible choice. Finishes are covered in the guide to the finish of a marble top.

What to do, in order

• take the limescale remover out of a bathroom that has a stone top: it matters more than all the other decisions together;
• dry the band around the basin, the one daily gesture that breaks the circle;
• clean with a neutral soap, not with products chosen for the room rather than for the material;
• tackle limescale at source, which means water hardness, and not on the stone that shows its mark;
• on damage already done, tell the two apart: an absorbed stain is treated with a poultice, an etched area recovers only by removing material, as in the guide to re-polishing in place.

How we work

We select the block and work the stone in house, and the finish of a top is decided before cutting: the only moment when the choice costs nothing but a decision. We do not use resin to reinforce slabs: across a large surface what is needed is continuous support, and the mesh on the back is already a good backing. It counts in a case like this, because a recovery job then works on the stone and not on a film over it. For a project supply the route is the Contract section; the contacts reach the people who follow the work, and the tables show how we work when there is only one piece.

Frequently asked questions

Can I use a limescale remover on a marble top if I rinse it off at once?

No. The acid works the moment it touches the surface and the rinse always comes afterwards: it takes away the product, not the calcium carbonate the product has already dissolved. Etching is not a question of how long it sat there, but of the fact that it got there.

Is the problem absent on quartz or porcelain?

It changes, but the problems do not vanish. Quartz-based composites are not calcium carbonate, so acid does not etch them as it etches marble, but they contain binders that some products attack. The useful rule stays the same: the cleaner is chosen by reading the material, not the room.

How can I tell etching from limescale, without instruments?

Run a finger over a film of clean water: limescale feels like a roughness sitting on top and eases as you rub, while etching is smooth and lifeless and does not change. And look along the surface: limescale is lighter than the stone, etching is the stone without its gloss.

Request a quotation The contract division

This page describes assessment and selection criteria; it quotes no prices, no response times and no company case histories. The compositions cited are those declared by the manufacturers in the data sheets of two products on the market — a domestic sanitising limescale remover (sulfamic acid and formic acid) and a professional descaler for sanitary ware (hydrochloric acid in the 5-15% band, pH below 2) — and hold for those products, not as a general figure for the category: the valid figure is always the one on the sheet of the product in hand. EN 13755 (water absorption of natural stone at atmospheric pressure) is cited for its subject matter and without reproducing numerical values, which sit in the paid text. The labelling and ingredient-publication duties are those of Annex VII to Regulation (EC) No 648/2004 on detergents. Assessing an individual case is for whoever can see the top.