Gradients in Japanese Prints

Bokashi is a Japanese technique for hand-applying a gradient to a moistened printing block.

According to Wikipedia, "The best-known examples of bokashi are in the 19th-century ukiyo-e works of Hokusai and Hiroshige, in which the fading of Prussian blue dyes in skies and water create an illusion of depth."

"In this print by Hiroshige, bokashi is used in the foreground, at the horizon, in the sky, on the priest's robes, and in the square cartouche."