Flow-vis paint: why do F1 teams use it during pre-season testing?

During pre-season testing and F1 practice sessions, you may spot several teams applying a fresh coat of bright paint to their cars — commonly known as flow-vis.

The often luridly-fluorescent fluid is made up of coloured powder and paraffin that allows aerodynamicists to analyse the airflow over one or several areas of a car while it’s on track.

Flow-vis will often be put on major aero surfaces such as the sidepods, rear wing and front wing and its application is a delicate task: too much will create puddles that can impact the airflow, while too little can make it almost impossible to collect any data at all.

Drivers then have to dash out of the pitlane before the paint dries. As they drive, the bright paint is pushed across the bodywork in streaks, exposing how the air is flowing around the car. It can be so revealing that some teams have used darker UV paint that’s less visible.

Once the paint is dry within a handful of laps, drivers return to the pits so analysis can begin.

“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,” former Williams and Ferrari engineer Rob Smedley told F1. “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.”