The safest way to de-ice a car is to start the engine, set the heater to the windscreen with the air-con on and the rear demister running, spray de-icer on the glass, then clear it with a plastic scraper once the ice softens. Clear every window, both mirrors, all lights, the number plates and any snow on the roof before you set off. Never pour boiling or hot water on the windscreen, and do not leave the car running unattended. Allow ten minutes rather than rushing with a peephole.
Why should you never use hot water on a frozen windscreen?
The RAC warns against pouring hot or boiling water onto the windscreen because it can crack the glass, and adds that doing it repeatedly weakens the glass. The sudden temperature difference stresses the screen, and any small stone chip can spread into a crack. Even if the glass survives, the water runs down onto the wipers and door seals and refreezes, often worse than before.
Leave the kettle in the kitchen. Lukewarm water is a last resort, and a de-icer spray is better.
What tools should you keep in the car for winter?
- De-icer spray. The RAC suggests de-ice aerosols in place of water and notes that a high-quality spray will not damage paintwork, rubber or plastics.
- A sturdy plastic scraper with a straight, undamaged edge. The RAC advises against cheap, poorly made scrapers and makeshift tools such as bank cards or CD cases.
- A soft snow brush for the roof and bonnet, so you are not dragging the scraper over paint.
- A microfibre cloth to wipe the inside of the glass once it clears.
- Winter screen wash rated for low temperatures, so the washers do not freeze.
What is the safe step-by-step morning routine?
- Check the wipers are off before starting the engine, so they do not try to sweep frozen blades and damage the motor or rubber.
- Start the engine and stay with the car. Set the heater to the windscreen, turn on the air-con to dry the air, and switch on the heated rear and front screens if fitted.
- Brush off snow from the roof first, then the windows, bonnet and lights.
- Spray de-icer across the glass, mirrors and lights and give it a minute.
- Scrape gently with the edge flat to the glass, working from the top down. Do not scrape plastic convertible windows or headlight lenses; let de-icer and heat do the work.
- Free the wiper blades gently from the screen once loosened.
- Wipe the inside of the glass if it is misted, and wait until every window is clear before driving.
What does the law say about clearing your car?
Rule 229 of the Highway Code says that before you set off you must be able to see, so you must clear all snow and ice from all your windows. It also says you must ensure lights are clean and number plates are clearly visible and legible, that mirrors should be clear and windows demisted thoroughly, and that you should remove all snow that might fall off into the path of other road users. That includes the roof: a sheet of snow sliding onto the windscreen under braking is dangerous for you and anyone behind.
The RAC also warns about "frost-jacking", where thieves target unlocked, unattended cars left running on driveways. It notes that many insurers may not cover a car stolen this way, and that you can be fined for leaving the engine running in certain areas.
How do you stop the car freezing in the first place?
The Met Office explains that frost forms on clear winter nights when the temperature of a surface falls below zero, and notes that a windscreen can frost even when the car's thermometer reads above freezing. Glass cools faster than the air, so a cold, clear forecast is your cue to prepare:
- Fit a windscreen cover the night before, tucked into the doors.
- Park facing east if you can, so the morning sun reaches the screen.
- Lift the wipers off the glass or leave them clean, so blades do not freeze to it.
- Treat the door seals with a rubber conditioner, so doors do not freeze shut. Our guide to cleaning and conditioning car door seals explains how.
- Keep the inside dry, as moisture inside the car freezes on the inside of the glass too.
Does clean glass really make de-icing easier?
Yes. Ice and condensation cling to dirt and the greasy film on the inside of the windscreen, so a clean screen clears faster and stays clearer when the heater kicks in. Late autumn is a good time for a thorough clean inside and out, plus wax or sealant protection for the paint before the gritters come out. Our full interior and exterior valet, from £80, includes all the glass, and our winter car care routine for Derbyshire roads covers the rest of the season. We work across Derby and the surrounding area, Monday to Saturday.
Sources
- GOV.UK: The Highway Code, driving in adverse weather conditions (rules 226 to 237)
- RAC: How to de-ice your car
- Met Office: What is frost and ice?
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