F1 Testing: What is flow-vis paint and why is it crucial in Bahrain?

The 2025 Formula 1 season gets underway in Bahrain, with all 10 teams gathered on track for the first time this year for pre-season testing.

However, you may notice paint splashed across the liveries during the next three days in Sakhir, as testing also heralds the return of flow-vis paint.

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These aren't artistic flourishes though; they hold the key to unlocking performance secrets. This mysterious paint, called flow-vis, plays a crucial role in pre-season testing, offering valuable insights into a car's aerodynamic performance.

But what exactly is flow-vis and why is it so crucial? Let's find out.

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What is flow-vis and why is it important

Flow-vis, short for flow visualisation, is more than just paint; it's a window into the invisible forces shaping a car's behaviour on the track. This special blend, made of fluorescent powder mixed with light oil, usually paraffin oil, acts as a temporary sensor.

Engineers apply the paint to specific parts of the car that they want to investigate. While the paint is still wet, the car is driven out of the pit area and onto the circuit. As the car speeds up and takes corners, the airflow interacts with the paint and causes it to streak and dry in unique patterns.

These patterns act as a visual map, revealing crucial information about how air flows over the car's surface and highlighting areas of separation, turbulence, and efficiency.

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After the car is returned to the garage, engineers take photographs and begin to examine the painted areas. This data is gold dust for them, as it provides insight into how the flow interacts with crucial components like the wings, diffuser, and underfloor of the car. It also confirms the results seen in CFD (computational fluid dynamics) or wind tunnel testing.

Using this data, engineers can make targeted adjustments, such as fine-tuning wing angles, modifying bodywork elements, or experimenting with different configurations.

Engineer Rob Smedley, who previously worked for Ferrari and Williams, explains how flow-vis works:

"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."

How to watch F1 pre-season testing on TV

Coverage of F1 pre-season testing from the Bahrain International Circuit will be live on Sky Sports and Sky Go in the UK.

Broadcast details vary depending on your location. Please check below to see how you can catch the action.

F1 TV Pro subscribers can also tune in for pre-season testing in select regions.

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Written by

Sheona Mountford - F1 Journalist

Sheona Mountford is a motorsport journalist specialising in F1. As a writer and contributor, she covers a wide range of motorsport series from F1 to F1 Academy, responsible for breaking news, live race coverage and in depth analysis of the sport and the culture around it.

View full biography

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