After he removed the water bottle from his truck, Amuchastegui saw it had burned two holes in his front seat.
Last month, Dioni Amuchastegui—a battery technician with Idaho Power—was sitting in his truck during his lunch break when he noticed something funny out of the corner of his eye.
“At first I thought it was dust, but the window was rolled up so there was no wind,” he told TODAY. “Then I noticed that light was being refracted through a water bottle and it was actually smoke.”
After he removed the water bottle from his truck, Amuchastegui saw it had burned two holes in his front seat. Intrigued, he decided to see if he could recreate the entire scenario—safely, of course—with his company, which he posted on its Facebook page.
During the experiment, he quickly realized how hot the area around the water bottle had become—around 211 degrees.
That’s because “a round plastic bottle filled with clear water can act as a lens that concentrates the sun’s energy on one point,” according to Amuchastegui’s video on his company’s Facebook page. The result? Extra, directed heat.
After the video garnered more than 285,000 views on Facebook, the Midwest City Fire Department in Oklahoma confirmed that leaving bottled water in your car could be risky on a sunny day.
Granted, the conditions have to be just right, meaning the bottle has to be rounded, full of clear liquid, and sunlight has to pass through it at exactly the right angle, David Richardson, spokesperson for the Midwest City Fire Department in Oklahoma explains in a video. With those conditions, the concentrated light can even exceed 400 degrees.
You don’t have much to worry about if the bottle is only half full or empty, your car is moving, or if the sun is shining through tinted windows, he says. Watch him recreate the effect on a piece of paper below.
While chances are extremely slim your water bottle will incinerate your car, you may want to be safe and avoid leaving a full one in your car on a sunny day. Better yet, scrap the bottled water in general and invest in a reusable one instead.