Every winter someone cracks a windscreen with a kettle. Every winter someone else scratches theirs with a scraper full of grit. Frost is routine in the UK and there is a right way to deal with it.
Never use hot water
Glass expands when heated. Pour boiling water onto a cold windscreen and the outer surface expands while the inner does not. On a screen with an existing chip, that is very often the moment it becomes a crack across your field of view.
Warm water is safer than boiling but still a bad habit: it refreezes within minutes, and now you have a sheet of clear ice instead of soft frost, plus frozen door seals.
What works
- Start the engine and put the blowers on the screen, on cold air first, then warm as the engine heats. Cold air first avoids thermal shock.
- Use a proper de-icer spray on the outside while the blowers work from inside. It melts from the top surface down.
- Scrape only once the ice has softened. Use a plastic scraper, held flat, and keep it clean — a scraper dropped in the gutter and picked up again is full of grit.
- Clear the whole screen, both mirrors and all windows. Driving with a letterbox-sized hole is an offence and, more to the point, dangerous.
- Clear snow off the roof too, or it slides onto the screen at the first junction.
Do not scrape a dry, dusty screen
Frost bonds road dust to the glass. Dragging a scraper across that is dragging grit across glass under pressure. It is exactly how windscreens end up with fine scratches that flare into a starburst every time a car comes the other way at night.
Stopping it forming in the first place
- A windscreen cover is the least glamorous and most effective option there is.
- Park facing east if you can — the first sun does the work for you.
- Keep the inside of the glass clean. A filmed screen holds condensation, which freezes on the inside and is far more annoying to clear.
- A glass sealant makes ice release more easily and improves wet-weather visibility as a bonus.
The inside of the screen
Interior frost means moisture in the cabin. Common causes are wet mats, a blocked pollen filter, a leaking door seal or simply recirculation left on. Dry the mats, run the air conditioning to dehumidify even in winter, and clean the inside of the glass properly — the oily film from interior plastics holds moisture and makes it worse.
A dedicated glass cleaner and two cloths — one to clean, one to buff — will do more for winter visibility than anything else.
Wipers
Never run wipers on an iced screen. The blade tears on the ice, and a torn blade smears for the rest of the winter. Lift them off the glass overnight if frost is forecast, or at least free them by hand before switching them on.
Before you start
Always read the label on the product you are using and follow the instructions on it for dilution, application and safety. Work in the shade on cool paint, and test anything new on a small, hidden area first — particularly on trim, wraps and finishes you are not familiar with.
Not sure which product fits the job? SWAG Fast Lane asks three quick questions and puts the right kit together for you.