How do I get stains out of a composite granite sink?

Composite granite is ground stone bound in a resin, and it is the resin that stains — it is a polymer, and polymers absorb pigment from tea, turmeric, coffee and red wine. Hard water leaves scale on top of that. Both come off, but they need a method rather than a rinse, and light-coloured sinks need it more often.

What you'll need

• Cream cleaner
• Bicarbonate of soda
• Soft cloth or a non-scratch sponge
• Thin bleach (optional)
• White vinegar or a limescale remover (optional)
• Baby oil or a proprietary composite conditioner (optional)

Step by step

1. Work out whether it is a stain or scale.A brown or coloured mark is a stain in the resin. A white, chalky bloom, worse on a dark sink, is limescale sitting on top. They need opposite treatments, and treating scale as a stain gets nowhere.
2. Do the whole bowl, not the mark.Cleaning one patch of a composite sink leaves a clean patch in a dull bowl, which looks worse than the stain did. Whatever method you use, take it over the entire surface.
3. Start with a cream cleaner.A mild cream cleaner on a damp non-scratch sponge, worked over the whole bowl, rinsed thoroughly. This alone deals with most everyday marking and is the routine that stops stains setting in the first place.
4. Move to a bicarbonate paste for a set-in stain.Bicarbonate of soda mixed with a little water into a paste, spread over the stained area, left twenty to thirty minutes, then worked gently with a soft cloth and rinsed. It is mildly abrasive at a level composite tolerates.
5. Use diluted bleach for stubborn tea and turmeric.Fill or half-fill the bowl with water and add a capful or two of thin bleach, and leave it a few hours or overnight. The dilution matters — the point is a long soak at low concentration, not a strong application.
6. Never leave neat bleach in contact.Undiluted bleach sitting on composite can lighten or dull the surface permanently, which is a worse mark than the stain. Dilute it in a bowl of water and rinse thoroughly afterwards.
7. Treat limescale with acid, not abrasive.White vinegar or a proprietary limescale remover, left to work, then rinsed. Scrubbing scale off a composite surface with anything abrasive scratches the surface and makes the next lot of scale grip harder.
8. Deal with the white bloom on a dark sink.A very light film of baby oil or a proprietary composite conditioner on a dry sink, buffed off with a cloth, restores the depth of colour on a black composite. It is cosmetic and it lasts a few weeks, but it is what makes an old black sink look new.
9. Rinse and dry after every use.The single habit that makes the biggest difference. Composite stains and scales because things are left sitting in it — a teabag, a pan of turmeric-stained water, or simply hard water drying in the bowl.

Common mistakes

• Using a scouring pad or wire wool — It scratches the resin surface. Scratches then hold stain and scale far more readily than the original smooth surface, so the sink gets worse from that point onward.
• Leaving neat bleach in the sink — It can permanently lighten or dull composite. A long soak in heavily diluted bleach does the same job without the risk.
• Cleaning only the stained patch — You end up with a clean patch surrounded by an evenly grubby bowl, which draws the eye more than the stain did.
• Leaving a teabag or a turmeric pan in the bowl — These are the two things that stain composite fastest and deepest. Thirty seconds of rinsing prevents an hour of soaking.

Keeping on top of it

• Rinse and wipe the bowl dry after washing up (daily)
• Cream cleaner over the whole bowl (weekly)
• Limescale treatment in a hard water area (monthly)
• Diluted bleach soak for accumulated staining (as needed, a few times a year)
• Oil or conditioner on a dark composite sink to restore colour (every few months)

Questions people ask