What European pigment helped popularize blue aizuri-e prints in the 1820s?

The European pigment that helped popularize blue aizuri-e prints in the 1820s was Prussian blue.

Prussian blue was a synthetic pigment imported into Japan from Europe. Compared with older blue colorants such as indigo and dayflower-petal dyes, it offered a more vivid, stable blue and a wider range of tones. Its arrival helped make prints dominated by blue—known as aizuri-e, or “blue printed pictures”—especially attractive to artists and buyers.

The pigment became closely associated with the great landscape prints of the late Edo period. Katsushika Hokusai used it in Thirty-six Views of Mount Fuji, including The Great Wave off Kanagawa, while Utagawa Hiroshige employed it extensively in his own landscapes. Layering ink and using bokashi gradation allowed printers to suggest waves, mist, sky, and distant mountains even with a restricted palette.

Prussian blue did not simply replace every other blue, and aizuri-e could include small areas of another color. The key distinction is that the new European pigment gave artists a powerful technical and commercial alternative to traditional natural dyes, helping landscapes become a major ukiyo-e subject.