Black, anthracite and dark grey composite sinks look superb when they're new, so it's frustrating when the bowl starts to look chalky, grey or patchy. The good news is that the most common cause is a build-up on the surface, which can be cleaned off. The less good news is that some marks are damage to the material itself, and no cleaner can undo that. Working out which you have saves time, money and a lot of scrubbing.
The five usual causes
1. Limescale and hard-water deposits
This is the most common reason a dark sink turns white. When hard water dries, it leaves a thin layer of minerals behind, and on a black sink even a very thin layer shows up as a pale haze. Sink makers point out that these deposits also soak up colour from tea, coffee and food, which is why a "white" sink can also look greyish or brownish.
Signs: a chalky film that's worst around the plughole, under the tap, on the drainer and along the waterline. It feels slightly rough when dry, and it built up gradually.
2. Soap and cleaning-product residue
Washing-up liquid, spray cleaners and soapy water that aren't fully rinsed away can dry into a dull, smeary film. Combined with hard water, it turns into a stubborn grey coating.
Signs: a patchy, streaky film that may feel slightly greasy or slippery rather than chalky.
3. Heat damage
A very hot pan or tray placed straight on the bowl or drainer can leave a pale mark in the surface itself.
Signs: a sharp-edged pale patch, often roughly the shape of a pan base, that appeared suddenly. It feels smooth, and nothing you clean it with changes it.
4. Chemical damage
Bleach, drain unblockers, oven cleaner, paint-brush cleaner and solvents such as acetone or white spirit can discolour composite, especially if they're spilt and left to sit.
Signs: blotchy, faded or bleached-looking patches, sometimes in a drip or splash pattern, where a product was poured or left.
5. Wear and fine scratches
Abrasive pads, scouring powders and pans dragged across the bottom of the bowl leave fine scratches. These scatter light, so the worn area looks paler and greyer than the rest of the sink. Scratches also trap limescale and dirt, which makes the effect worse.
Signs: a dull, slightly lighter area, usually in the bottom of the bowl, that looks worse in raking light.
Quick check: can it be cleaned off?
| What you see | Likely cause | Can cleaning fix it? |
|---|---|---|
| Chalky film, worst near the plughole, tap and drainer | Limescale | Yes, with a limescale remover suitable for composite |
| Smeary, patchy film that feels slightly greasy | Soap or product residue | Yes, with warm water, washing-up liquid and a thorough rinse |
| Sharp-edged pale patch that appeared suddenly | Heat damage | No. Contact the sink maker or retailer |
| Blotchy, bleached patches where something was spilt | Chemical damage | No. Contact the sink maker or retailer |
| Dull, paler area in the bottom of the bowl | Wear or fine scratches | Partly: deposits in the scratches can be cleaned, but the scratches stay |
The patch test
If you're not sure, clean one small patch first, for example a strip next to the plughole. Use the method below, then dry the sink completely and compare the patch with the area around it. If it comes up darker and more even, the whitening is a deposit and the rest of the sink should respond in the same way. If it looks no different after a couple of careful attempts, the mark is probably in the surface itself, so stop cleaning and check your sink's guarantee.
How to fix whitening caused by limescale or residue
- Wash off residue first. Clean the whole sink with warm water and a little washing-up liquid, then rinse well. On its own this often brings back some of the colour.
- Treat the limescale. Wearing gloves and eye protection, in a well-ventilated room, spray Astraclean undiluted over the affected areas and spread it with a soft cloth, sponge or brush. Do not breathe spray. Keep it off the tap, because it isn't suitable for plated metals.
- Wait 2–5 minutes, then scrub lightly in small circles with a soft sponge or nylon brush. Use an old toothbrush around the plughole.
- Rinse thoroughly and dry. Judge the result once the sink is completely dry. For heavy build-up, repeat or leave the product on a little longer before scrubbing.
For more detail, including what to avoid, see How to remove limescale from a composite sink.
If it's damage
Heat marks, chemical marks and scratches are in the material, not on it, so cleaning can't remove them, and harder scrubbing will only make things worse. Many composite sinks come with a long manufacturer's guarantee, so it's worth contacting the maker or the retailer with photos. Some sink makers also sell a care or restorer product for their own material, so ask what they recommend.
Keeping a dark sink dark
- Rinse and dry the sink after use, especially last thing at night.
- Let pans cool, or use a trivet. Don't put hot pans straight on the bowl or drainer.
- Keep bleach, drain unblocker and oven cleaner away from the sink, and rinse any spill immediately.
- Use soft cloths and sponges, never abrasive pads or powders.
- Deal with limescale little and often. See our granite composite sink care routine.
Frequently asked questions
Why is my new black sink already going white?
In a hard-water area, limescale can start to show on a dark sink within weeks, especially if it's often left wet or a dish rack sits on the drainer. A chalky film near the plughole and tap is usually limescale and should clean off. A sudden, sharp-edged mark is more likely heat or chemical damage.
Can a sink that's gone white be made black again?
If the whitening is limescale or cleaning residue, removing it usually brings back the original colour. If it's heat damage, chemical damage or wear, cleaning can't reverse it, so contact the sink maker or retailer.
Will bleach get rid of the white marks?
No. Bleach doesn't remove limescale, and many composite sink makers warn that it can discolour the surface. Never mix bleach with a limescale remover or any other cleaner.
Does Astraclean work on grey and white composite sinks too?
Yes. Astraclean is made for composite, granite and quartz sinks in black, white and other colours. Don't use it on unsealed natural stone or on acid-sensitive surfaces such as marble, terrazzo, enamel or plated metals.