Blue has long proved a problem for artists. There are few blue materials in nature that can serve as pigment for painters. During the Renaissance period artists used a pigment called natural ultramarine, lauded for its rich and striking appearance.

In this Nature Video, we visit London’s National Gallery to hear the story of natural ultramarine; where it came from, how famous painters used it, and how advances in chemistry during the 19th century enabled the production of a synthetic version which revolutionized painters’ palettes.

Read Nature's review on the exhibition: Science of colour: Hue and eye