This is a companion page to the post on green tea ice cream and mochi ice cream.
Definition of suminagashi from this source:
A paper decoration design, *ryoushi soushoku similar to a marble design. A few drops of ink, *sumi are poured onto the surface of water and then a sheet of *washi is dropped on top. The flowing ink creates a wave pattern on the paper. While various types of paper are used for the process, *ganpishi is used most often. In addition to black ink, vegetable dyes such as indigo, *ai and safflower red, *beni are also used. The earliest example of suminagashi can be found in the early 12c anthology Sanjuurokuninshuu from Nishihonganji, Kyoto. Since ancient times the suminagashi technique has been used on cloth as well as paper. A similar technique is also used on lacquer and ceramic wares.
When the pattern is ready, a sheet of paper is made to adhere to the water surface and then pulled up, rinsed and dried.
Go to the post on gelato al tè verde e mochi con gelato (green tea ice cream and mochi ice cream) to read the related story.