Surface is smooth and lustrous, and is colored with black (crack) ink to create a beautiful pattern.

"Kannyu" is a small crack in the surface of the glaze due to the difference between the shrinkage of the base material and the glaze. Sumi Crackle Glaze (Japanese: 墨貫入 sumi-kannyu) is made by penetrating the cracks in the glaze called "kannyu". The more you use it, the more it will develop new Kannyu.

Since it has some water absorption properties, darker colors such as tea or coffee will soak into the perforated part of the pot. You may hear a cracking sound at the beginning of use, but you can use it with no problem.