This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.

ST. LOUIS, MO (KTVI)– If you plan on firing up that car defroster as soon as you hop in the car, you will want to hear a warning from an area auto glass technician.   He says blasting heat on a frozen window can cause it to crack or shatter.

Adam Kaufman is an auto glass technician with the Glass Doctor.   The replacement and repair business is located at 9400 Manchester Road in St. Louis County.   Workers are busy as soon as weather winter hits.

“Every morning we get blasted with calls,” said Adam Kaufman, auto glass technician.

When it comes to the windshield, an existing crack or nick can lead to bigger problems if hot air from a defroster is fired on the frozen windshield.

“The crack is immediately going to travel towards that heat,” explained Kaufman.  “It`s going to hit that crack, that chip, and start spreading it straight up your windshield.”

Rear windows are made differently than windshields.  They are more likely to shatter.

“It`s just like dropping an ice cube in a hot glass of water,” said Kaufman.  “The cube explodes.  It`s the same thing with the back window on your car.  It gets too hot too quick and it explodes.”

Kaufman suggests warming your car for a few minutes with your vent before firing the defroster full blast on maximum heat.