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
Turmeric stains in onyx come out with a hydrogen peroxide poultice: wipe up the spill, wash the area, then cover the yellow stain with the poultice for 24 to 48 hours. Curcumin, the yellow pigment in turmeric, fades under UV light, so a few days of direct sunlight on the stain often finishes the job.
First, check what you are dealing with
- Yellow or orange mark: turmeric or curry. Follow the steps below.
- Yellow mark with an oily halo: curry oil too. Do a solvent poultice after the peroxide.
What you need
- pH-neutral dish liquid
- Hydrogen peroxide
- Flour, talc or diatomaceous earth
- Plastic wrap and tape
- Plastic scraper
Step by step
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 yellow stain, 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 yellow stain is lighter but still there, repeat up to three times.
Let the sun help
Curcumin, the yellow pigment in turmeric, fades under UV light, so a few days of direct sunlight on the stain often finishes the job.
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, which can leave a pale patch in the stone.
When to call a professional
If a yellow shadow persists after poulticing and sunlight, a restorer can treat it. Onyx needs a restorer who works with it regularly: it is softer and more fragile than marble and easy to over-polish.
Understanding turmeric and curry 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 needs a restorer who works with it regularly: it is softer and more fragile than marble and easy to over-polish.
Good to know
Turmeric on onyx shows through the stone when it is backlit. Gentle 3% peroxide and sunlight are the safest first steps.
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 · Turmeric & curry stains on every surface