Some kind of blue

Next week is time for the local Jazz Festival, and to prepare I switch my background music back to Miles’ iconic album. In addition, I have been made aware that I seem to be making blue my go-to color. On a slightly related note, it turns out that blue is a very hard color to make.

I spy, with my little eye, something blue…

It seems weird that blue would be hard to make. It’s so prominent in nature. The sky is blue. The ocean is blue. Blue jays are blue. Blue eyes are blue.

But as it turns out, blue pigment is very rare. Butterflies and birds with a blue color aren’t blue because their wings or feathers contain blue pigment, but because of nanostructures that reflect and diffract light in such a way that interference amplifies blue wavelengths, while cancelling out the others.

Macro photo of a butterfly wing
Butterfly wings aren’t actually blue, they’re just pretending to be. (Image Grover Schrayer/Flickr)

A blue pigment, however, absorbs all wavelengths except blue. Light absorption occurs when a photon supplies an electron with enough energy to jump to a higher energy band. As red light has the lowest energy, only electrons with a narrow energy gap can be excited. Only a few molecules have the right structure for this to happen. Absorption of red light is crucial for a blue pigment, and therefore it’s a rare thing.

Illustration of the bandgaps for blue and red absorption
Blue light has enough energy to allow an electron to jump a larger energy gap then red light. Last time someone explained light absorption to me, they did it in the form of interpretive dance. It made so much sense.

Out of the blue

Because of their natural rarity, the design of synthetic blue pigments is of high interest for science and industry. The bluest blue was created by accident, by Mas Subramanian, a solid state chemist who wanted to create a material with the combination of electronic and magnetic properties for microchips. One of his ideas didn’t lead to anything particularly useful for fast computers, but it was very blue.

Blue powder
The bluest blue: YInMn (Photo by Ian Allan)

The blue dream

Where did this quest for blue originate? Blue is most people’s favorite color; it symbolizes depth, stability, and serenity; and as it is the color of the sky and the sea, painters love it. True blue flowers are non-existent (violets are purple, people), even though horticulturists and scientists have tried endlessly. And even though blue food is unconsciously associated with toxins and spoilt food, some scientists’ life goal is to create true blue food coloring, rather than current food coloring that seems more green.

The blue man group: a blue man pouring yellow paint
And I’m sure that Blue Man Group would appreciate a bluer skin. (Photo: Blue Man Group)

While artists, foodies, and flower lovers dream of the truest blue, I’ll go back to some sweet tunes and feeling slightly melancholic. I mean… Blue.

Read more about blue in this Science feature.

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