The eruption of Taal Volcano has caught many by surprise—particularly those spending their weekend in Tagaytay to simply enjoy the city’s cooler temperatures. Images of vehicles fleeing the area have flooded social media. They’re like scenes straight out of the movie Dante’s Peak. Cars are caked in ash, their occupants able to see outside only through a portion of the windshield cleaned by the wipers.

It may seem like common sense operating the wipers when you can’t see anything. We do it when it rains. But a volcanic eruption and the resulting ashfall have vastly different effects to automotive glass than heavy precipitation.

When you flick that stalk, each stroke of your wiper blades pushes the ash against the glass. Continuing to operate your wipers will soon heavily scratch your windshield, eventually making it translucent to opaque. That’s because volcanic ash is highly abrasive stuff. According to the United States Geological Survey, volcanic ash is composed of glass shavings, rock fragments and other hard minerals and crystals formed from the depths of the earth and shot out of a hole in the crust under immense heat and pressure.

Volcanic ash is composed of glass shavings, rock fragments and other hard minerals and crystals formed from the depths of the earth

The best way to avoid this is to simply not drive at all and wash your vehicle with pressurized water when the ashfall has subsided. But if it’s absolutely necessary for you to set off in your car, avoid using the wipers if you can help it. If the weather is dry, ash will simply cascade down your windshield. However, if you do need to activate the wipers, do so while constantly spraying washer fluid. This will create a slippery layer between the blade and the glass. While this is no guarantee that your windshield won’t get scuffed, it will certainly help keep it transparent for as long as possible.

In addition, refrain from rolling your windows down. The rubber strips on your doors will have the same effect as your wipers and may scratch your glass. It is also best practice to top up your washer fluid before you drive, and to bring jugs of water so that you’ll have something to wash your windows with.