How to Remove Water Spots from a Windshield and Car Windows

Park next to a lawn sprinkler for one night in July and you can come back to a windshield covered in white dots that no car wash will remove. The same thing happens with well water, and with hard tap water on a black car left to dry in the sun. The heat bakes the mineral onto the glass, and once it is baked, glass cleaner and even clay bars slide right over it. People routinely spend money on new windshields for this. A jar of paste and half an hour usually fixes it.

Why it is worse on cars than at home

A shower door gets spotted slowly, at bathroom temperature. A windshield gets spotted in direct sun, where the water evaporates in minutes and the minerals fuse to the hot glass. That is why auto water spots feel rough to the fingertip while shower spots feel smooth, and why the usual home remedies, vinegar and lemon, do so little on a car.

What you need

• A-MAZ Water Stain Remover, the same non-acid paste sold through glass shops for exactly this job
• A Gripper Pad, which has a handle and covers more glass per stroke than a hand pad
• A spray bottle of water and two clean microfiber cloths
• Ultra Gloss Sealant to keep the spots from coming back

Step by step

1. Work in the shade on cool glass. Hot glass dries the paste before it can work. Wash the glass first so you are not grinding grit into it.
2. Apply and rub. Dampen the pad, scoop a little paste, and work a section about a foot square in overlapping circles with firm pressure. Mist with water to keep the paste wet. You will feel the roughness disappear as the spots lift.
3. Check as you go. Wipe a section clean and dry with a cloth and sight across it at a low angle. Baked-on spots often take two or three passes; that is normal, not a sign it is not working.
4. Do the mirrors and side glass. They spot the same way and clean the same way.
5. Rinse, dry and seal. Rinse the glass, dry it fully, then apply a thin coat of Ultra Gloss Sealant with a cloth and buff until smooth. Sealed glass beads water instead of holding it, so the next sprinkler pass rinses off with the hose. On a windshield the sealant also improves wiper action in rain.

Tinted windows

Factory tint is inside the glass and is not affected. Aftermarket tint film is applied to the inside surface, and water spots are on the outside, so the paste never touches the film. Customers with dark aftermarket tint have used A-MAZ on the exterior glass with no trouble; just keep the paste on the outside.

Paint and chrome

Water spots on paint are a different problem, and a paste designed for glass is too aggressive for clear coat. Keep A-MAZ to the glass, chrome and polished metal trim. On chrome and stainless trim it removes the same spotting and light oxidation; work with the grain on brushed finishes.

If the spots are more than a season or two old, read how to tell water stains from etching before you start, so you know what result to expect.