Sailor is also an expert on ink. The Nano Sei-boku Ink is product with the latest technology of sailor. The ink is pigment based to give the blueblack colour. All colour molecules in the ink are at the nanometer level which guarantee that the ink will never block the fountain pen.The smoothness of the ink flow is also better during writing.
The ink is also highly water proof. During the experiment, it shows no spreading of the ink after dropping water on dried ink.
The cartridge version provides a length of up to 1000m writing. It also easy to use and to store. It fits well to all kinds of pencil cases.