Bluish black Kobaien ink sticks ( 青墨 )

Sumi ink that appears black with a bluish tint is called Seiboku ( Bluish ink ) . Soot, which is collected when pine or vegetable oil is burned at uneven combustion temperatures, varies in particle size.

The ink made from such soot can vary in color from heavy black to blue-gray. In addition to those in which the soot itself appears bluish, there are also those that are colored with indigo or other bluish colors.