Before you try anything: always speak to a professional before cleaning, treating or applying any product to your stone. Every slab is different, and the wrong product can cause permanent damage. Contact us or a qualified stone restorer first.
Quick answer
Coffee stains in onyx are tannins that have soaked into the stone. Blot, wash with pH-neutral soap, then draw the stain out with a hydrogen peroxide poultice covered with plastic for 24 to 48 hours. Coffee is acidic too, so if a pale, dull ring remains once the brown has gone, that part is an etch and needs polishing, not more poulticing.
First, check what you are dealing with
- Brown or tan ring, surface still smooth: a stain. Follow the steps below.
- Pale, dull or slightly rough ring: an etch from the coffee's acidity. See fixing etching below.
- Both: remove the stain first, then deal with any dull mark.
What you need
- Paper towel
- pH-neutral dish liquid
- Hydrogen peroxide
- Flour, talc or diatomaceous earth
- Plastic wrap and tape
- Plastic scraper
- Gloves
Step by step
Blot, do not wipe
Soak up any liquid with paper towel straight away. Wiping spreads it across a bigger area.
Wash the area
Clean with warm water and a few drops of pH-neutral dish liquid, rinse and dry with a soft cloth so you can see what is left on the onyx.
Test first
Try the mixture on a hidden spot of your onyx (inside a cut-out or under an overhang) and check the finish after it dries.
Mix the poultice
Stir an absorbent powder (plain flour, talc, diatomaceous earth or whiting) into hydrogen peroxide (3% from a pharmacy for fresh stains, or 12% from a hairdressing or pool supplier for older ones) until it has the consistency of peanut butter.
Apply it
Spread it 5 to 6 mm thick over the coffee ring, extending about a centimetre past the edge. On onyx, stick to 3% peroxide and check after 24 hours rather than 48.
Cover and wait
Cover with plastic wrap, tape the edges and poke a few small holes so it dries slowly. Leave it 24 to 48 hours until completely dry: the drying is what pulls the stain up into the powder.
Remove and rinse
Lift the dry poultice with a plastic scraper, rinse with clean water and dry the onyx. If the coffee ring is lighter but still there, repeat up to three times.
What not to use on onyx
- Vinegar, lemon juice or "natural" citrus cleaners: they etch onyx.
- Scourers, steel wool and abrasive creams on a polished surface.
- Mixing cleaning chemicals, especially bleach with anything else.
- Bleach: it rarely lifts tannin stains from stone and can damage the finish.
When to call a professional
Call a stone restorer if the stain survives three poultices, covers a large area, or has left a dull etch ring you cannot polish out. Onyx needs a restorer who works with it regularly: it is softer and more fragile than marble and easy to over-polish.
Understanding coffee stains on onyx
Architectural onyx is banded calcite. It is less absorbent than limestone, but its translucency means a stain can show from both sides of a backlit piece.
Onyx is calcite and usually highly polished, so a drop of lime or wine leaves a dull etch that catches the light immediately.
Onyx needs a restorer who works with it regularly: it is softer and more fragile than marble and easy to over-polish.
Good to know
Coffee on an onyx bar or table is easy to see with the backlight on. Onyx is soft and often resin-backed, so keep poultices gentle and short, and leave anything stubborn to a restorer.
Stop it happening again
Whether yours is honey, white, green and pink banded onyx, often backlit, repairing it fixes today's mark; protecting it stops the next one. Our clear Stone Protection Film sits over the surface, so acids cannot etch it and liquids cannot soak in. Onyx is usually polished, so Gloss film is the natural match and keeps its reflective depth. It is installed across Sydney with a 10-year written warranty.
How we protect onyx · Stain removal guide · Coffee stains on every surface