What is the fluorescent paint on F1 cars at Bahrain testing?

It is known as “flo-vis paint” and you will see many F1 cars smeared with it during testing.

The paint is a fluorescent powder mixed with a light oil and is used to help understand a car’s aerodynamics.

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Rob Smedley, an ex-Ferrari and Williams engineer, explained: “You paint it liberally on the car, the car then goes out and as it’s moving up to speed and going through a cornering condition, the paint dries as the light oil evaporates and you end up being able to visualise, very clearly, what sort of flow structures you've got.

"When we then analyse that – we’re usually looking for things like separation, as in where the flow's separating and we’re not getting decent flow structures across the surfaces of the car. That can then tell the aerodynamicists a lot about what's going on upstream of that, and hopefully that helps them to rectify certain problems on the car.

“You’ll often then see the teams looking to cover a car that’s been running flow-vis with screens when it comes back into the pits. 

“The dream for the other teams is to try and get bits of information about a competitor, so the screens just stop rivals getting pictures of your car with the flow-vis paint on it, which is going to tell a competitor a story about your car, or maybe tell them information which is key to what they want to do as well.”