It seems that the paint on red cars fades more quickly than any other car colour. Is there a reason why?
鈥� Cars painted red appear to fade faster because red paint is inherently more vulnerable than other colours are to the ultraviolet radiation in sunlight, which can accelerate the decomposition of its chemical structure. The paints used on modern cars are mostly thermoplastic polymers, composed of large and complex molecules, very much like those that comprise living tissue. They are susceptible to degradation when exposed to ultraviolet. So long-term and continual exposure to direct sunlight will break down the paint molecules and the colour will gradually fade.
To protect against fading, paint manufacturers usually add an ultraviolet stabiliser, but this will only slow down the degradation, not prevent it altogether. As red tints naturally reflect light at the red end of the visual spectrum, they consequently absorb more radiation at the opposite blue end, right into the ultraviolet frequencies. As a consequence, their molecules are exposed to a proportionately greater dose of ultraviolet and degrade faster than green, grey and blue colours.
Advertisement
Red also tends to contrast most strongly with the background environment, which usually comprises a medley of greens, greys and dull browns, beneath an (occasionally) blue sky, all lit by the light of a yellow sun. Therefore, any effect which lessens the contrast between the paint and the background colours will be all the more noticeable, and the brighter the red, the more obvious the fading.
Hadrian Jeffs, Norwich, Norfolk, UK
鈥� You often see this effect on old printed posters in downmarket shop windows, where the signs are seldom replaced. The original colours are lost, with red being the first to go, followed by the other colours, until eventually, the sign becomes just a faded blue.
鈥淥n old posters the red colour is always lost first, and eventually it becomes just a faded blue鈥�
Red light has a longer wavelength and thus less energetic photons than does blue light. The blue pigment reflects the blue and absorbs the lower energy red light. The red pigment reflects the red and absorbs the higher energy blue, and this added energy breaks down the red pigments faster.
R. J. Best, Fremont, California, US