Santorini, Mykonos, Lindos – all Greek towns famous for their characteristic quaint white houses. They are picture postcard perfect and attract a lot of tourists. However, bringing tourism to the town is not the reason they look the way they do. There is science behind the charming white housing.
Santorini, Greece, a popular tourist destination. (https://commons.wikimedia.org/wiki/File:Oia-Santorini-Greece.jpg), accessed 13/05/2020
Although the Sun may look a yellowy orange when we look at it, sunlight is actually white. Light follows different colour mixing rules to those you would have learnt during art mixing paint. When the spectrum of colours of light are mixed instead of making brown, like you would expect, it makes white.
Red, green and blue are the primary colours of light, they mix very differently to paint. (http://www.texample.net/tikz/examples/rgb-color-mixing/), accessed 13/05/2020
When white light is refracted through a prism it separates into its different wavelengths (colours) (https://commons.wikimedia.org/wiki/File:Prism_by_Godzilla.png), accessed 13/05/2020
The reason we see objects as certain colours is due to the wavelengths that they absorb or reflect. The colours we see are the colours which are reflected or transmitted (through a filter). For example, a red jumper appears red as it reflects red light and absorbs the light from the blue/violet end of the spectrum. If you shone blue light on it, it would appear black as no light would be reflected and all would be absorbed.
This means for an object to appear white it must reflect all the light that hits it. Whereas a black object absorbs all the light that reaches it. This could be important for many situations. For example, if you were putting on a play or fashion show and you wanted the colours of the costumes to really pop you would have to make sure you had the correct lighting.
Reflective surfaces, like mirrors, also reflect all light. A white surface will scatter the light it has reflected much more than a mirror would. Therefore, white walls don’t reflect images like a mirror. This is why it is easier to look at a white surface when the Sun is shining directly on it rather than look in a mirror.
Looking at the sun directly or when reflected in a mirror can really damage your eyes (https://www.pexels.com/photo/bokeh-car-mirror-dirty-mirror-evening-sun-1466951/) accessed, 13/05/2020
So back to our classic Greek houses. Yes, they look delightful and charming, not to mention neat and co-ordinated. However, it is not the strict planning regulations that lead to this uniform white colour. It is in fact down to the necessity to keep cool. The white paint reflects the sunlight, keeping the houses a more bearable temperature during the hot Grecian summers. Architects are now adopting this age-old principle and applying it to modern passive design to create more sustainable and environmentally friendly buildings.
- To experiment for yourself with how colour can affect temperature change watch this video.
- For more experiments on passive design have a look at the Designing a Passive Building STEM Project.