Fact check: Pouring hot water on your windshield could cause cracked or shattered glass

McKenzie Sadeghi, USA TODAY
·4 min read

The claim: Pouring hot water on a windshield will quickly defrost your vehicle

The icy winter storm across the U.S. has brought snow to 100 million Americans from the South to East Coast, causing hazardous road conditions and car troubles such as icy windshields.

While authorities have urged people to stay home and avoid unnecessary travel, one social media user recently took to Facebook to offer some alleged advice on how to defrost car windows that have been frozen by the ice and sleet.

The user claims dumping scorching hot water on your windshield can be more effective at clearing the glass windshield.

"Pour hot water on your windshield & it’ll defrost faster thank me later," reads the Feb. 14 post with over 12,000 shares.

USA TODAY reached out to the Facebook user for comment.

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Hot water will crack windshield

Pouring hot water on your vehicle's windshield to melt the ice could actually crack or shatter the glass due to extreme temperature changes.

"While it may be tempting to quickly thaw out your windshield with hot water, it’s a very bad idea. Rapid temperature changes in glass can cause it to crack, and automotive glass is no exception," according to the site for the Glass Doctor a glass repair and replacement company.

Not only does using hot water to de-ice a vehicle result in cracks on the windshield, but it can also damage paintwork when the boiling water melts off protective wax and leaves a white watermark stain, according to Prestone.

Problems arise when the glass expands at a quick rate only in spots where the hot water was splashed while the rest of the windshield remains freezing cold. When the hot bits of the screen meet up with the cold bits, it results in a crack in the windshield.

A survey by the Automobile Association found that people age 18 to 24 are more than twice as likely to use boiling water to defrost their car than the general population and 1 in 20 risks a cracked windscreen by pouring boiling water on it.

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How to properly defrost vehicle

AAA recommends using a properly operating heater, as a cold engine will not produce the warm air needed to defrost a vehicle.

Once the vehicle is operating at the right temperature, climate control should be set to full defrost rather than bi-level, but it should not be turned on full blast right away.

The drastic temperature change can result in glass cracks, and it is best to allow the windshield to gradually warm up, according to AAA. The defroster should also be using fresh air, not recirculated air.

To clear snow from the windshield, it is suggested to use a long-handled household broom or a snow rake designed specifically to be used on cars so that the glass is not scratched in the process.

A de-icer spray can also be created by making a solution mixing two-thirds rubbing alcohol and one-third water and spraying the solution on the frozen windshield, according to Safelite AutoGlass.

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Our rating: False

The claim that pouring hot water on your windshield will defrost it faster is FALSE based on our research. Auto glass companies warn that doing this can result in cracked or even shattered glass. It is recommended to use a properly operating heater to de-ice a frozen windshield and a long-handled broom or specialty snow brush to clear away snow.

Our fact-check sources:

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This article originally appeared on USA TODAY: Fact check: Pouring hot water on your windshield could damage glass