What synthetic blue pigment was used in The Great Wave off Kanagawa?

The synthetic blue pigment used in The Great Wave off Kanagawa was Prussian blue.

Hokusai used Prussian blue prominently in the print, including the deep tones of the wave and the distant Mount Fuji. The pigment was a major innovation for Japanese ukiyo-e artists because it was more resistant to fading than indigo, a traditional blue commonly used in earlier prints.

Prussian blue had been developed in Europe and began arriving in Japan through Dutch trade. It was imported from around 1820 and became available in larger quantities by the late 1820s. Its adoption helped create a “blue revolution” in Japanese landscape printing during the 1830s.

The Great Wave was among the first Japanese prints to feature the pigment, and its intense colour contributed to the image’s visual power. Hokusai combined Prussian blue with other colours rather than using it alone; the print’s effects also depend on black outlines, pale washes, and carefully carved woodblocks.

Ultramarine, cobalt blue, and indigo are all real blue pigments, but they are not the canonical answer for the distinctive synthetic blue associated with this print. Prussian blue is also known as Berlin blue or, historically in Japan, bero-ai.