How Extreme Temperatures Affect Your Car Glass

A chip can sit in a windscreen for weeks without changing, then turn into a long crack on the first frosty morning or the first hot afternoon. What sets it off is a sudden change in temperature, not the weather itself. If your screen has a chip, a stone chip repair before the weather turns is the simplest way to keep it in one piece.

Why Hot and Cold Weather Cracks Glass

Glass grows very slightly as it warms up and shrinks as it cools. When the whole windscreen warms or cools at the same pace, it copes well. Problems start when one part changes temperature much faster than the rest, such as a patch of glass hit by hot air from the vents while the edges are still frozen. The glass is then pulling against itself, and it gives way at its weakest point. A chip is that kind of weak point, and so is damage close to the edge of the screen, where the glass is held tight in its frame.

Cold Mornings

• Never pour hot or boiling water on a frozen screen. Hot water on icy glass can split a chip open in seconds. Let the demister soften the ice, then clear it with a plastic scraper, never anything metal.
• Warm the glass gradually. Start the engine and point the heater at the screen on a low setting to begin with, rather than blasting hot air at frozen glass.
• Use a heated windscreen if you have one. It warms the glass evenly across the screen, which is far kinder to it than hot air aimed at one spot.
• Free the wipers before you switch them on. Blades frozen to the glass can tear, and a torn blade drags grit across the screen.

Scrape the whole screen, not just a patch in front of you. Rule 229 of the Highway Code requires you to clear all snow and ice from all your windows before you set off.

Hot Days

• Cool the car down slowly. After it has stood in full sun, open the windows for a minute before you turn the air conditioning to full cold, and keep the vents off the windscreen at first.
• Do not rinse hot glass with cold water. Washing the car in the midday sun, or turning a cold hose on a hot screen, gives the glass the same shock as hot water on a frozen one.
• Park in the shade when you can. A shaded spot or a sunshade behind the windscreen keeps the cabin cooler, so there is less of a jump when the air conditioning comes on.

If Your Screen Already Has a Chip

A chip is where temperature damage starts, so the best time to have one repaired is before the first frost or the first heatwave. The repair takes about 20 to 30 minutes once we arrive, and if the chip can be repaired, we will have a technician with you within 24 hours. Until then, cover it with clear tape and follow the tips above.

If a Crack Has Already Spread

Once a crack runs out from a chip, the glass cannot be repaired and the windscreen needs replacing. We fit new windscreens at your home or work across London, Essex and Hertfordshire, and replace rear and side glass too.

We are a local, family owned business based in N22. Call us on 07426 801611, or send a photo of the damage to us on WhatsApp and we will give you a price for your car.