Water Spots

Water spots, watermarks, or hard watermarks are most often caused when calcium in water forms droplets and the calcium or limescale forms a ring around the edge of the droplet.

This will leave limescale rings on the car, which can be removed with a watermark remover, however, as the limescale is forming, there is a caustic reaction which can cause etching to paintwork and glass which may require polishing to remove.

Rainwater is naturally soft, and therefore wants to absorb minerals that are on your car's paintwork. The issue of watermarks can be far worse when the car is contaminated with dust, cement or plaster powder as these can be highly reactive.

What it means

Water spots are the ring-shaped marks you see when water has dried on your car and left something behind. The water itself evaporates, but minerals from hard water, road film, screenwash, sprinklers or even acid rain can remain as a visible spot. Sometimes this is just a light deposit sitting on top of the surface. In worse cases, especially on hot panels, the droplet can act like a little lens and the residue can lightly etch into the clearcoat or glass, leaving a mark that does not wipe off.

Why it matters

• Lets the finish down: A clean car covered in water spots still looks messy in the sun, especially on dark colours and glass.
• Can become permanent etching: If strong minerals or contaminants are left to bake on, they can mark the clearcoat or glass so that only polishing or even replacement will fully remove the damage.
• Shows issues with wash and rinse routine: Heavy water spotting often points to hard rinse water, poor drying technique, sprinklers, tree drip or regular parking where overspray lands on the car.
• Affects coatings and protection: Ceramic coatings and waxes help, but they do not make the car immune. Persistent, strong spotting can still mark coatings and will need safe removal.

Where you’ll see it

You will see water spots mentioned on detailing inspections, glass polishing quotes and aftercare advice. Typical phrases include light water spotting on horizontal panels, etched water spots on glass or hard water marks from sprinklers. Bonnet, roof, boot lid and tops of bumpers are common areas, along with windscreens and side glass that have been left to air-dry or sit under drips.

Context

Water spots sit in the same family as stains, bird mess etching and fallout marks. The key question is whether you are dealing with a simple deposit on top of the surface or true etching in the paint or glass. Light spotting often responds to proper washing, dedicated water spot removers or mild chemical decontamination. Heavier etching may need machine polishing on paintwork and specialist polishing on glass, always within safe limits. Prevention is largely about avoiding letting dirty water dry on the car: sensible wash technique, using better rinse water where possible, drying with clean towels or air and keeping away from sprinklers and tree drip.

Common mistakes

• Letting rinse water or sprinkler spray dry repeatedly on the car instead of drying it or moving it out of the spray pattern.
• Scrubbing at stubborn water spots with harsh pads or abrasives, creating wash marks or scratches while the underlying etch remains.
• Assuming ceramic coatings make the car immune to water spots, then neglecting basic washing and drying because it is “coated”.
• Ignoring early spotting on glass and paint until it has etched badly, when simple chemical removal would have worked if tackled sooner.

Written by Danny Argent. Last updated 21/11/2025 16:52