It is an all to common sight on the roads to witness a car that once sported a proud red paint now looking like a sad, pink version of its older self. To an extent, all car exteriors can become faded, but red cars seem to be affected by this to a much greater extent. This phenomena isn’t a coincidence and the culprit for this is the glowing sphere of plasma at the centre of our Solar System, the Sun. While it provides life for everything on this planet, the Sun is red paints worst enemy.
To understand why, we need to look at the electromagnetic spectrum. The is the scale of electromagnetic radiation. The scale displays radiation in order of energy, or wavelengths, from short to long. At the weakest end you have radio waves with long, slow wavelengths. Opposing this at the other end is the high energy gamma rays, with the shortest wavelengths. Right in the centre of the spectrum is visible light, which reaches our eyes.
Visible light also has different wavelengths. All of the colours that we see closer to the vibrant Ultraviolet end of the spectrum (blues and purples) have more energy due to the shorter wavelengths. However, the lowest energy form of visible light is the colour red. Who’s longer, less-energetic wavelengths make it a much more docile colour.
So why is this important? It’s important due to how light interacts with the world around us. The colour an object appears is because that’s the only colour reflected from the object, with all the others being absorbed. If you’re looking at a green surface, this material is absorbing all of the other colours except green, reflecting only this colour to our eyes.
This is crucial to understanding why some car colours fade faster than others. When light hits a red car, the paint will absorb all the high energy colours accept red, breaking down the molecules in the paint as it attempts to handle the influx of energy. Over time, this molecular break down dulls the glowing red finish. This also explains why other colours take longer to fade, such as white, where all wavelengths are reflected.
There are several preventative measures one can take to stop this fading from happening: waxing offers some protection, and there are also companies that will fit a film to stop the UV light from reaching the paint.