Windscreen chip repair: how it works and when it helps

A windscreen is laminated: two sheets of glass bonded to a clear plastic interlayer. A stone usually damages only the outer sheet, which is why a chip can often be filled rather than the whole screen replaced. A good repair restores strength to the damaged area, stops the chip from spreading and makes it much less visible.

What happens during a repair

1. The damaged area is cleaned and any loose fragments removed.
2. A bridge tool is fixed over the chip and air is drawn out of the break.
3. A clear resin is injected under pressure so that it fills the legs and voids of the chip.
4. The resin is cured with ultraviolet light and the surface is finished flush with the glass.

Most chip repairs take well under an hour and the car can be driven straight away. The repair will not always be invisible: a small mark often remains, but it should be clear and should not catch the light the way an open chip does.

Is your chip suitable?

Size, type, position and age all matter. Small bullseye and star chips away from the edges are the classic repair; long cracks, damage near the edge and damage in the driver's central field of view usually are not. Our guide to repairable windscreen cracks goes through the checks a repairer makes.

Protecting a chip until it is repaired

• Put a piece of clear tape over the chip to keep out water and dirt. Dirt in the break makes a clean repair harder.
• Avoid blasting hot air from the demister onto a frozen screen, and do not pour hot water on it. Sudden temperature changes are a common reason a chip turns into a crack on a cold morning.
• Do not slam doors and go easy over speed ramps and potholes.
• Avoid washing the car at high pressure near the chip.

Will insurance pay?

Many comprehensive policies in Ireland include windscreen cover, and insurers usually prefer a repair to a replacement because it costs less. The details vary by policy, so read our guide to windscreen cover and your no claims bonus before you ring.