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There are various terms used for liquid ink, such as bokueki(墨液), bokuju(墨汁), bokuteki(墨滴), etc. However, all of these refer to liquid ink, and the specific name used often varies by manufacturer. On this site, we will primarily use the term "sumi ink" (unless a product's official name is bokuju or bokuteki).

To distinguish between liquid ink made from grinding a solid ink stick and commercially produced liquid ink, we refer to the former as "ground sumi ink."

Solid ink sticks are made by mixing and kneading soot with animal glue (膠, Nikawa), then molding and drying them. Liquid sumi ink, on the other hand, is made by mixing soot (primarily carbon black) with an adhesive component and adding water to create a liquid. Today, there are also liquid sumi inks produced with the same soot and glue as solid ink sticks. The difference from solid ink sticks lies in the addition of stabilizers to prevent soot from settling or solidifying, and preservatives to prevent mold and decay.

Sumi ink offers several advantages: you can start writing immediately after pouring it into a container, and its consistent color means there's no need for color matching. However, on the flip side, the presence of preservatives and stabilizers can have drawbacks, such as causing brushes to deteriorate more quickly or hardening if not washed immediately. Many people also use sumi ink directly in their inkstones, but these preservatives can coat the inkstone's surface, making it difficult to grind sumi ink in the future. We often get asked, "Is it okay to add sumi ink to ground sumi ink?" Yes, adding commercial Liquid ink to sumi ink is fine. However, we do not recommend grinding a solid ink stick directly into commercial Liquid ink. Similar to what happens with an inkstone, the grinding surface of the ink stick can become coated with preservatives, making it impossible to grind effectively.

Sumi ink has become indispensable for modern calligraphy. To make the best use of it and prolong the life of your tools like brushes and inkstones, we recommend a few simple practices: separate brushes for Sumi Ink and Liquid Ink, and use an inkwell (墨池, bokuchi) instead of an inkstone for commercial sumi ink.