A Small Star, a Big Crack: Why Your Windscreen Repair Can't Wait for Spring

A windscreen chip is one of those jobs that is easy to file under “I'll get to it.” It is small, it does not affect the radio, and the car still starts. Then the first properly cold morning arrives, you hit the demister, and the little star you have been ignoring since summer suddenly has legs. In my experience, that is when the phone calls start — usually from a driver standing next to a crack that is now longer than their hand.

A chip is a break, not a blemish

Modern windscreens are laminated: two layers of glass with a plastic sheet bonded between them. That construction is brilliant for safety, but it means a chip is not just a mark on the surface. It is a small fracture with air and moisture inside it. The plastic layer may still be holding the screen together, but the damaged area is weaker than the glass around it.

That matters because windscreens do not just sit there looking pretty. They are part of the car's structure, they support the dashboard and airbag loads, and on plenty of modern cars they carry cameras and sensors behind the rear-view mirror. A tiny defect in the wrong place is not simply an appearance issue.

Why cold mornings finish the job

Glass does not like sudden temperature changes. On a frosty morning the outer surface is cold, then you fire up a hot demister and warm one patch of the screen while the rest is still chilled. Add the flex that comes from a stiff chassis, a pothole, a speed hump or simply closing a door, and a chip that was stable in July can start to run.

There is also water to consider. Moisture gets into the fracture, freezes overnight and expands. Repeat that a few times and the crack creeps outward. Grit and salt thrown up by traffic do not help either — they are abrasive, and a screen that is already damaged is more vulnerable to the next stone strike.

This is why a chip that has survived months of mild weather can become a crack in the space of one cold week. It is not bad luck. It is physics.

The quick checks worth doing now

Start by cleaning the area so you can see what you are dealing with. Use a torch at a low angle and look at the chip from both outside and inside. A fingernail is a useful tool: if it catches on the damage, you have a chip or a small pit. If you can see a line running away from it, you have a crack, and that changes the conversation.

Here is a simple routine:

• Mark the ends. Put a small piece of tape at each end of any visible line and photograph it with your phone. Check again in a few days. If the line has moved past the tape, it is spreading.
• Check your view. Damage directly in the driver's line of sight is taken more seriously than a chip near the edge or low down on the passenger side. It is not just about size; it is about what you can see.
• Look at the edges. Cracks that reach the edge of the screen are usually replacement territory. The edge is where the glass is bonded to the body, and a crack there can affect strength.
• Keep it dry. A piece of clear tape over a chip is a temporary measure, not a repair. It keeps water and grit out until you can get it looked at.

Repair or replace? What fitters actually look at

A resin repair is often possible on a small chip, typically around the size of a 25p coin, provided it is not in a critical viewing area and has not started to crack. The repairer cleans out the damage, pulls a vacuum to remove moisture, injects resin and cures it with UV light. It restores a good deal of strength and stops most chips spreading, although it may leave a faint mark. That is normal.

Replacement becomes the sensible option when the damage is larger, when there are several chips close together, when a crack is running, or when the damage sits in the driver's primary line of sight. Cars with camera systems behind the screen may also need recalibration after a replacement, which is an extra cost and another reason not to leave things late.

UK insurers usually have a windscreen section on comprehensive policies. Repair often attracts a smaller excess — sometimes none — while replacement has a set excess. Check your policy before you book, and ask whether a repair will affect your no-claims discount. Many insurers treat a repair differently from a full replacement, but the details vary.

The money side is simple

A resin repair is usually a fraction of the cost of a new screen. Replacement can run into hundreds of pounds before you add sensors or calibration, and that is before you count the time without the car. The frustrating part is that many chips could have been repaired cheaply weeks earlier. Waiting does not save money; it usually moves you from the repair column to the replacement column.

What to do before the next hard frost

Book the repair now if you have a chip that has been hanging around. Until then, avoid blasting a hot demister straight onto a frozen screen — let the car warm up gradually. Use a proper de-icer or a scraper rather than hot water, which is a excellent way to turn a small chip into a large crack. Avoid pressure-washing directly at the damage, and do not slam the doors or boot harder than usual.

And if the chip is in your line of sight, is spreading, or has a crack running from it, do not wait for a convenient weekend. Get it assessed. A windscreen is one of those parts where the cheap fix has a deadline, and cold weather is very good at enforcing it.