New blues

640px-Tsunami_by_hokusai_19th_centuryYOU have probably seen The Great Wave off Kanagawa – the Japanese woodblock print of a huge, foaming wave about to engulf a group of small boats. It’s no surprise that the picture is mostly blue; it is a wave after all.

However, it is part of a series of images called Thirty-six Views of Mount Fuji by the artist Hokusai, and if you flick through them, you will notice that nearly every one is predominantly blue. That might seem strange, until you realise that in 1830, when Hokusai began printing these works, blue was rather a new thing. The Prussian blue he used had been introduced into Japan just a few years earlier, giving artists their first blue pigment that was bright, attractive and lasting.

“Historically, blue has been a big issue for artists; there are very few natural blue colours,” says materials scientist David Dobson at University College London. These days, we have plenty of blue dyes, which, being soluble, are ideal for colouring materials uniformly. But the insoluble blue pigments needed for paints, printing inks, ceramics and plastics are still rare. That is why, when Dobson realised that he might be able to create a new one based on a mineral that can exist only at the immense pressures found 500 kilometres beneath Earth’s surface, he was very much up for the challenge.

The colour blue has proved such a problem to recreate that most ancient cultures don’t seem to have had a word for it – Homer famously describes the “wine-dark” sea. Only the ancient Egyptians are known to have had one, and it’s probably no coincidence that they alone were able to produce a blue pigment. Egyptian blue was used widely until the Middle Ages when the recipe was lost and artists had to resort to either azurite or ultramarine (see “True blue“). Both were made from naturally occurring minerals, the latter from lapis lazuli. This was exorbitantly expensive, explaining why blue tended to be reserved for high-ticket items such as the Virgin Mary’s robes.

 

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Picture credit: wikipedia.