Will Hot Water Crack A Frozen Windshield? | Winter Tips
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Will Hot Water Crack A Frozen Windshield?

Will Hot Water Crack A Frozen Windshield?
Posted in Tips On By Aaron

Will hot water crack a frozen windshield or windscreen? We go through why you shouldn't pour boiling water over your car's windshield.

Picture this. It's 6am and you've just woken up to get ready for work. You look outside and see yours and your neighbour's cars have frozen over due to the winter weather. This is definitely not a rare occurrence for those living in the UK. You now how multiple options. 

1. Wait for the ice to thaw naturally. Not recommended if you're in a rush!

2. Use a de-icer spray to remove all of the ice off your windshield

3. Scrap off the ice using a specialised squeegee or brush

4. Use your cars heated windscreen technology to thaw the ice

5. Pour warm or hot water over the windshield

Did you know it's illegal to drive if your windshield and other windows are obstructed with ice? Rule 229 of the Highway Code states that your "windscreen and other windows must be clear of ice, snow and any obstructions". Failing to follow this rule can result in a £60 fine and up to three points on your licence due to endangering other road users.

An image of ice frozen against a glass surface

What are car windshields made of?

Early 1900s cars windshields were made with ordinary glass, but this caused injuries during crashes as the glass shattered. Both modern cars, vans and any other vehicle on the road have windshields made by laminated glass, which is a type of safety glass that holds together when shattered. These windshields have interlaced polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), or Thermoplastic Polyurethane (TPU) which helps to bond the laminated glass together and gives it high durability and strength. 

Will hot water crack a frozen windshield?

This is a common question that many people ask during the winter months. And the answer is simply no, pouring warm or hot water over a laminated glass windshield can not crack it. This is because of how laminated glass is created and protected by the materials mentioned above. 

An image of a kettle with hot water inside

So why do experts recommend us not to do it?

This is due to how water can expand when frozen. If you have a small unnoticeable crack on your windshield and you continuously pour water over it, it will become filled. When refreezing happens either during the day or at nighttime, the water stuck in the crack will freeze and expand, causing the small crack to get larger and more noticeable. If this process happens enough times your windshield will need to be repaired. This is the same process that happens with potholes on the road, as they are constantly subjected to rain and freezing conditions which causes them to expand and grow larger. 

So what's the easiest solution to thaw a frozen windshield?

De-icer is the quickest and easiest way to thaw a frozen windshield. As a Ford owner, I personally find the quickest way is to switch on the heated windscreen function and spray some de-icer at the same time on the side windows. This thaws out the car within 5 minutes and is safe and ready to drive. However, if you don't have the heated windscreen function (check out our which cars have heated windscreen technology post), the quickest and easiest way is still to use a de-icer and ice scraper to spread the spray across all the frozen surfaces.

An image of a de-icer branded spray being used on a frozen car windshield

Established in 2009, Stable Vehicle Contracts are a UK based premium vehicle leasing company. We are part of a large, privately owned, Volkswagen and Audi dealership group with over 25 sites. Stable Vehicle Contracts has the ability to offer the very best car and commercial vehicle lease deals and thanks to our partners in the trade, we've become leaders in the supply of cars and commercial vehicles through leasing. Give us a call today on 0151 728 4711 or visit our Special Offers page to see what deals we have on.