Suminagashi (墨流し) is a dyeing process. It is translated in English as "marbling".
Suminagashi is easily recognizable due to the liquid-like patterns that occurs as a result of the dyeing technique.
In creating this design, the craftsman pours water into a long shallow basin. One or more colors (depending on the design) of a specific type of hydrophobic paint is added to the water.
The artisan will then use a set of tools to pull the paint around. The process is so delicate that, in some cases, hair is the only equipment used.
Finally, to complete the process, the fabric is briefly set onto the paint (and water) and the design transfers onto the fabric.