Here’s How Modern Convertibles Use Special Pigment So Their Leather Seats Don’t Burn Your Butt

As durable and aromatic as leather can be, it does have some flaws as automotive upholstery. It need frequent care, requires touch-up if it grows worn, gets cold in the winter, and can grow uncomfortably hot in the summer sun. While heated seats have somewhat solved the cold-in-winter complaint for eons, several manufacturers now offer sun-rejecting treated leather that can take the experience of sitting on a sun-baked dark leather seat down from medically concerning to merely uncomfortable.

In principle, the primary enemy here is infrared radiation, that band of light with wavelengths between 780 nanometers and one millimeter. It makes up the bulk of sunlight’s irradiance, and sunlight infrared radiation is responsible for about 49 percent of Earth’s heating, so you can imagine what it can do to leather in the sun. If leather can be treated in a way that rejects some infrared and near-infrared radiation, it should stay cooler on hot days.

Believe it or not, this heat-rejecting leather isn’t that new. BMW has been using it for ages, including in the available leather seats on the 2007 3 Series Cabriolet. In BMW’s case, the treatment consists of a special infrafred-blocking dye and is still used today under the trade name Sun Reflective Technology. When it debuted, BMW made some impressive claims about its heat-rejection capabilities, so here they are in the automaker’s words:

Particularly appealing on the new 3 Series Convertible is the special leather that was developed for the seating upholstery. Modified color pigments serve to reflect the infra-red radiation by the sun, very effectively preventing excessive temperatures on the seat surfaces otherwise encountered in weather that would be perfect for open-air motoring. To achieve this, BMW is the first carmaker in the world to use Sun Reflective technology in its leather. Applying this process, pigments are embedded in the material during production to reflect infra-red radiation in sunlight in wavelengths of more than 720 Nanometers, significantly reducing the usual heating effect on the surfaces. All other qualities of the leather material remain unchanged. Sun Reflective technology is used both on the seat upholstery and on the armrests to prevent body contact with excessively hot surfaces. This new leather treatment is able to reduce surface temperatures on dark interior colors by up to 20 Celsius degrees (36 Fahrenheit degrees), and also offers advantages on light-colored upholstery, where the heating effect of sunshine is less severe, reducing the surface temperature by as much as 15 Celsius degrees (27 Fahrenheit degrees).

A claimed temperature reduction of “up to 20 Celsius degrees” is absolutely enormous for dark upholstery, but this technology itself isn’t hogwash. An indication that sun-reflecting seats work is the fact that Mercedes-Benz started offering sun-reflecting leather in the 2021 E-Class cabriolet, albeit with the more modest press release claim that it “remains up to 13 degrees Celsius [23.4 degrees Fahrenheit] cooler in direct sunlight.”

So, do these heat-rejecting leathers actually work? Well, Car And Driver put them to the test for 90 minutes in sunny, 77-degree weather against the leather seats in an NA Mazda Miata, and while the fancy German leather wasn’t exactly cool to the touch, it did make a meaningful difference.

By the end of the test, temperatures recorded from the BMW and the Mercedes were an average of 25 degrees Fahrenheit cooler than the Miata’s seats. That’s not to say you’d be perfectly comfortable sliding into the E-class or the M440i; the average seat temperature in those cars was still 123 degrees compared to 148 degrees in the Mazda. We also noticed that even though the E450 and M440i ended the test with the same average seat temp, the BMW’s leather stayed cooler for longer, with an average seat temperature of 114 degrees compared to 122 degrees in the E450. This could be due to the BMW pigments being more effective than the Mercedes-Benz coating, but we think it’s more likely due to the E450 having dark brown seats to the BMW’s light tan.

Not only does 25 degrees Fahrenheit [13.8 degrees Celsius] live up to Mercedes-Benz’s claim, at a resulting surface temperature of 123 degrees Fahrenheit, it can be the difference between “ouch” and “AAAAAAAAAHHHHHHHHH IT BURRRNNSSSSS!” We’ve come a long way from the days of being branded by all-metal seat belt buckles like cattle, and sun-rejecting leather is just another touch of modernity.

So, is there any coating you can apply to reduce the temperature of your leather seats after a day in the sun? In short, not really. In factory-applied applications, heat-rejecting leather relies on pigments rather than a topcoating, and while there are plenty of leather protectants that offer UV resistance, infrared-blocking isn’t in the cards. However, with several automakers now offering this heat-rejecting leather, there’s a chance this tech might make it to your driveway soon.

(Photo credits: BMW, Mercedes-Benz)

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