Etching, and what cleaning cannot fix

What etching actually is

Marble, travertine and limestone are calcium carbonate. Acid dissolves calcium carbonate. That is the entire mechanism and it is a chemical reaction rather than a cleaning problem.

When something acidic sits on the stone, it eats a microscopic layer off the surface. What is left is duller than the stone around it, because the smooth polished or honed surface has been removed and replaced with a rougher one.

It is worth sitting with what that means. The stone is not dirty in that spot. There is nothing sitting there to remove. The surface itself is gone, and cleaning a hole does not fill it in.

How to tell etching from a stain

People frequently spend months trying to clean an etch, so this is worth knowing.

A stain is darker than the surrounding stone, because something has soaked in. It usually darkens further when wet.

An etch is duller, not darker. On polished stone it reads as a matte patch where the reflection has gone. Wet it and it looks much the same, because there is nothing absorbed to darken.

Run a finger across it. An etch frequently has a slightly different texture, a faint roughness against the polish around it.

What causes it, and the list is longer than people expect

Food and drink

Wine, citrus of any kind, tomato, vinegar, coffee, most sodas. Anything that would taste sharp is acidic enough to etch.

Cleaning products, which cause most of it

This is the one nobody sees coming. Most general-purpose bathroom cleaners are acidic. So is almost anything marketed for soap scum, hard water or lime scale, which in this climate is exactly what people reach for.

Vinegar in particular gets recommended constantly as a natural cleaner, and on a marble floor it is one of the worst things you can put on it.

Other companies

We find etching that was put there by cleaning services, and it is not rare. A company that treats a stone floor like a tile floor, using the same acidic product that shifts hard water off ceramic, will etch travertine on the first pass.

What we do about it, which is tell you

Removing etching means honing and polishing the stone with diamond pads, cutting the surface back until it is level and then rebuilding the finish. That is refinishing, it is a genuine skill, and it is not what we do.

We clean and seal. Those are different trades that get confused because both involve somebody kneeling on a stone floor.

When what your floor needs is a refinisher, we will tell you that instead of taking the job and leaving you disappointed.

What cleaning and sealing does achieve on an etched floor is worth stating too. Everything except the etch marks improves, frequently substantially, and on a floor with a handful of etches in a large area that can be exactly the right answer. The marks remain and the floor around them looks considerably better.

We will point out every etch during the walkthrough and be clear that it is staying. Better said beforehand than explained afterward.

Scratches and worn finish

Same category and the same answer.

Traffic lanes on a polished stone floor lose their finish over years, abraded by grit underfoot. The surface has physically changed, which is why a traffic lane looks different from the stone beside it even when both are equally clean.

Cleaning removes the soil and the lane will still read differently, because the difference is finish rather than dirt. Restoring that is refinishing work.

Preventing it, which is the only real answer

• pH-neutral, stone-specific cleaners only. Throw out anything acidic and stop taking advice about vinegar
• Keep the stone sealed. It does not make stone acid-proof, it buys you the minutes between a spill and the damage
• Wipe spills immediately, particularly anything citrus or wine
• Coasters and mats under anything that might drip, in kitchens especially
• Tell whoever cleans your house, including a service, exactly what may and may not be used on the stone
• In a rental, leave the correct product and remove every alternative from the cupboard

None of that helps a floor already etched. All of it prevents the next one, which over a decade is the difference between a stone floor that stays beautiful and one that needs refinishing.

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