Water Spots on Your Car: How to Prevent and Remove Them
You wash the car, it looks perfect, and by the time it dries it is covered in faint white rings. Water spots are one of the most common frustrations in car care, and in large parts of the UK they are almost guaranteed if you wash the wrong way. The good news is that they are easy to prevent and, if you catch them early, easy to remove.
What water spots actually are
Tap water and rain both carry dissolved minerals, mainly calcium and magnesium. When a droplet dries on your car, the water evaporates and the minerals stay behind as a white or grey ring. That is a water spot.
How bad they get depends largely on where you live. Much of the south and east of England, including London, the Home Counties and East Anglia, has hard water with a high mineral content. Scotland, Wales and much of the north west have far softer water. If you wash your car in Essex, you will fight water spots far more than someone washing in Cardiff.
The three stages of a water spot
Water spots get worse the longer they are left. Detailers usually describe three stages.
- Surface deposits. Fresh mineral rings sitting on top of the paint or coating. These come off with the right product and no polishing.
- Bonded deposits. Minerals that have been baked on by sun and heat, or left for weeks. They need an acidic product and more patience.
- Etching. The minerals, or acidic rain and bird droppings, have eaten into the clear coat and left a small crater. No chemical will fix this. It needs machine polishing.
The whole point is to deal with spots while they are still in the first stage.
Why they appear more on some cars than others
Water spots show up most on dark paint, on glass and on horizontal panels such as the bonnet and roof, where water sits longest. They are worst in warm weather, when droplets evaporate in minutes, and after washing in direct sun, when the car starts drying before you have finished rinsing.
Ceramic coatings help, because water beads and runs off instead of lying on the panel. But the droplets that do remain still leave minerals behind, and over months those deposits can build up on the coating itself and dull its performance. We come back to that below.
How to wash without leaving water spots
Wash in the shade, on cool panels. Early morning, evening or an overcast day is ideal. If the panels are warm to the touch, wait.
Work in sections on hot days. Wash and rinse one area at a time rather than soaping the whole car and rinsing at the end.
Never let the car dry on its own. Air drying is how most water spots are made. Dry straight after the final rinse with a large, soft drying towel such as Silky Finish, blotting or gently dragging it across the panel rather than rubbing. Misting Ceramic Quick Detailer onto the wet panel as you dry gives the towel extra glide and leaves a slick, water-repellent finish. It works on wet or dry paint.
Reduce the water you have to dry. A rinse-off sealant such as Wet Coat is sprayed onto the wet car and rinsed off. It makes water sheet away in seconds, so there is much less left on the paint to evaporate and leave minerals behind.
Use filtered or deionised water for the final rinse if you can. In hard water areas this makes a noticeable difference. Some self-service wash bays offer a spot-free final rinse, and it is worth using.
Do not forget the glass. Spots on a windscreen are more than cosmetic, because they scatter light from oncoming headlights at night. A glass coating such as Vista makes water leave the screen far more quickly.
How to remove water spots that have already formed
Minerals are alkaline, so they dissolve in a mild acid. That is the principle behind every proper water spot remover.
- Wash the car first. Working on a dirty surface just drags grit around and adds scratches to the problem.
- Keep the panel cool and out of the sun. Acidic products should never dry on hot paint.
- For fresh spots, start with Ceramic Quick Detailer. It has a slightly acidic pH and a high SiO2 content, so it dissolves fresh mineral rings while leaving a layer of protection behind. Spray, wipe with a clean microfibre and buff.
- For heavier deposits, use an acidic shampoo at a stronger dilution. Bubble Shock is designed for this: at its weekly dilution it is a gentle wash, and at its stronger dilutions it dissolves mineral deposits from paint, glass and coatings. It also smells of Sicilian orange, which makes the job a little more pleasant.
- Let the chemistry do the work. Allow the product a short dwell time, agitate gently with a clean mitt, and do not scrub.
- Rinse thoroughly and dry straight away, so you do not create a fresh set of spots.
- Check under good light. If rings are still visible after two careful attempts, they are probably etched into the clear coat and need polishing. A finishing polish such as Fine Cut will usually remove light etching.
Water spots and ceramic coatings
A coating makes water spots less likely, but it does not make them impossible. There is also a less obvious effect. Regular washing with pH-neutral or alkaline shampoos slowly leaves a film of minerals on the coating. Over a few months the beading weakens and the car stops cleaning as easily, and it is easy to assume the coating has worn out when it is actually just clogged.
That is why Ultracoat recommends servicing a coated car every 6 months or 6,000 miles: a wash with an acidic shampoo such as Bubble Shock to remove the mineral build-up, followed by full decontamination. The coating's original properties come back. Between services, a spray sealant such as Ceramic Quick Detailer keeps the surface slick and the beading strong.
If you would rather have it done for you, accredited Ultracoat Pro studios carry out coating services.
Summary
Water spots are minerals left behind when water dries on your car, and in hard water areas of the UK they are part of everyday life. Wash in the shade, never let the car air dry, reduce the water left on the panels and dry it promptly. When spots do appear, remove them early with an acidic product before they have a chance to etch. And if your car is coated, a regular service keeps minerals from building up and dulling the finish.
To understand how coatings help with all of this, read what hydrophobicity is and why it matters, and for the full picture on looking after a coating, see six common myths about ceramic coatings.