Marble and acid

Why marble reacts to acid

Marble is mostly calcite. When acid touches it, the surface reacts and partly dissolves, leaving that spot duller or rougher than the stone around it. This is called etching.

Limestone, travertine and onyx contain calcite too, so they react in the same way. Granite is generally more resistant to common kitchen acids, but acidic cleaners are still unsuitable: some minerals can react, and hydrofluoric acid can attack silicate stones too.

Everyday items, hidden risks

• Lemon, orange and other citrus fruit
• Vinegar, salad dressings and tomato sauce
• Wine, soft drinks and coffee
• Bathroom cleaners and limescale removers

Etching or staining: how to tell

Etching changes the surface finish, leaving a dull or rough-looking mark. Staining changes the colour as a substance enters the stone; the colour depends on the substance.

A spill can cause both etching and staining, so appearance alone is not always enough to choose a treatment. The Natural Stone Institute describes both effects in its care guidance. See source below.

If something has just been spilled

Blot it straight away with a clean cloth. Do not wipe back and forth, which spreads it.

Rinse with plain water, then blot dry.

Do not reach for scouring powder, bathroom cleaner or the rough side of a sponge to remove the mark: it only dulls a wider area.

Prevention

Use coasters, and trays under oil and condiment bottles, on marble tops.

Clean regularly with a pH-neutral 7.0 cleaner.

A penetrating sealer improves stain resistance; it should not be relied on to prevent acid etching. Marble still needs care around acidic spills.

When to call a craftsman

Once a mark has dulled the surface, cleaning will not remove it. The stone needs restoring with the right polishing grade. Our craftsmen judge the depth of the mark and always prove a small area first.