Sumi (Chinese Ink) ()

Sumi refers to soot derived from substances such as lampblack or burnt pine, solidified by mixing with gelatin (solid sumi). It also refers to a black liquid made by grinding solid sumi with water against an ink stone. It is used for calligraphy and painting.

Liquid sumi ink is a colloidal suspension of amorphous carbon. Sumi sold commercially in this state is called bokuju (liquid sumi ink) or sumijiru (liquid sumi ink). Unlike ancient sumi, chemically synthesized substances are used as main ingredients in some cases of bokuju.


Remnants of ink writing and red ink are found on the oracle bones of ancient China.
It is considered that sumi ink was in use at the same time inscriptions of ancient Chinese characters on oracle bones and tortoise shells developed during the Yin Dynasty
Besides writing, it was also used in tattooing, and this later became a method of punishment. By the Han Dynasty, sumi was made into a round shape, called bokugan (round inkstick).

The oldest Japanese ink writing that exists today is said to be the character 'ta' (rice field), which was marked on a late second century clay pot unearthed from the Kaizo ruins in Ureshino-cho, Mie Prefecture (Mie Prefecture) (present-day Matsuzaka City).

The first mention of sumi in Japan was a description of Chinese sumi in "The Nihonshoki" (Chronicles of Japan). Inksticks made from burnt pine in Nara Wazuka during the latter half of the Nara period are considered to be the very first ones made in Japan. Production of inksticks made with lamp soot began during the Kamakura period. Production took place in various regions during the Edo period. However, artisans gathered in Nara, where the production had taken place since the ancient times. It continues as a traditional industry to this day. Currently, Nara and Mie Prefectures are the major producers.

Characteristics of sumi

Fresh solid sumi contains a substantial amount of water. Characteristics of animal glue is dominant, therefore it is highly viscous. Therefore, when used on paper, the shin (the core) (the stroke made with the brush) and the nijimi (the portion of calligraphic work that seeps outward through the paper, blurring the edges of the brush stroke) are difficult to distinguish. When sumi gets old and dry, the animal glue decomposes, and therefore the ink flows better. The ink color gains three-dimensionality, and it is said that variation in the ink color according to the brush movement, such as the shin and nijimi, takes on aesthetic expression. Such sumi is called 'koboku' (old inkstick) and they are highly prized. The more carefully the sumi is made, the longer it takes to dry.

Types of sumi

Depending on the soot, which is the main ingredient, solid sumi is divided into burnt pine ink and lamp soot ink. There are expressions such as red ink, seiboku (blue ink), purple ink and brown ink. However, all, except for the red ink, are basically black in color, and these expressions are used to describe the shades of color. The ingredient of the red ink is cinnabar, which is a naturally occurring mineral that is mined.

Burnt pine ink (seiboku)

Because of variations in the burning temperature, burnt pine soot has particle sizes that are uneven. Therefore, there is a wide range of ink color from dense black to bluish grey. Those that have a bluish hue are called seiboku (blue ink). As for the manufacturing method, pinewood pieces are burnt and the soot is obtained. For the blue ink, besides the soot itself having a bluish color, some may be further colored with indigo (plant).

Lamp soot ink

Lampblack has soot particles that are fine and even in size, and therefore it has luster and depth to its black color. As for the manufacturing method, it is made by putting oil and lighting a wick in a clay pot, and by collecting the soot that forms on the lid of the clay pot. For the oil, Chinese cozla is considered to be the most suitable, but others, such as sesame oil, soy bean oil, camellia and paulownia are also used.

Animal glue

Collagen (animal protein) extracted from animal bones, skin and tendons is used for gelatin in the production of sumi. High-quality binders use deer, but cows, pigs and rabbits are normally used, and fish is used for the inexpensive product. Sumi made with animal glue made from fish has a distinctive smell. Chemically synthesized resin (whose ingredients are similar to those of adhesives) may be used in order to make up for it.

Whether it's solid sumi or liquid sumi, the components of animal glue deteriorate over time.
This is called 'withering of the animal glue.'
When sumi is first made the animal glue is strong and elastic. When applied on paper, the difference between the shin (the part that's written with the brush) and nijimi is small. However, the animal glue withers with time, and the extent of nijimi increases, expanding the freedom of expression with the tones of sumi color. If there is a lot of water, then nijimi expands greatly from the line that is drawn.
This condition is called the 'scattering of sumi.'
Solid sumi where the animal glue has withered with time is called 'koboku.'
It becomes possible to create lively lines and give a sense of three-dimensional appearance as well as to express with unlimited colors. Therefore, it is indispensable, especially in works of light ink painting, and it is expensive.

Because the animal glue is animal protein, it becomes more viscous and turns into a gel at low temperatures, which is not appropriate for calligraphic work. Therefore, sumi needs to be used at temperatures above a certain level.

Sumi as a handicraft

Besides the technique to knead sumi, the shape of sumi is also important. A sumi mold engraver creates a wooden mold, and there are many different shapes.


During the 1880's, Seiji TAGUCHI, an elementary school teacher, came up with the idea of making liquid sumi when he saw his students grinding sumi with cold water during winter. He studied applied chemistry at Tokyo Vocational School (present-day Tokyo Institute of Technology), and he later invented bokuju. In 1898, he named it 'Kaimei Bokuju' (Kaimei liquid sumi ink) and commercialized it, and he founded Taguchi Company (present-day KAIMEI & Co., Ltd.) in Tsukudo Hachiman, Ushigome Ward (present-day Shinjuku Ward).

There are some bokuju that use industrially produced carbon black (carbon) (in some cases, this carbon has almost the same constituents as toners used in copy machines) when compared to naturally derived soot. In addition, there are those that use chemically synthesized, adhesive-like resin instead of animal glue.

In the case of bokuju made with an animal glue, a long drying time is necessary when adding a lining. If the drying time is short, then the sumi will scatter. In liquid sumi that's either thick or the animal glue has withered, there is an extensive scattering of sumi. Therefore, sprays that prevent such scattering are commercially available. It is necessary to be careful when applying a lining by oneself.

On preservatives

The animal glue contained in sumi is animal protein. It deteriorates quickly because it is a perfect breeding ground for bacteria. In order to prevent that, commercially available bokuju contains preservatives.

Solid sumi does not contain preservatives. Therefore, liquid sumi made by grinding does not last long, and it is necessary to use it up right away. The preservatives in liquid sumi deteriorate over time, and it is said that it decays in about two years. Rotten sumi emits a characteristic order of decaying animal, and since it damages the brush, the use of rotten sumi should be avoided.

Sumi with strong preservatives can possibly damage the brush. Therefore, when using an expensive brush, one should avoid using low-quality liquid sumi. In addition, there is a cautionary note stating that liquid sumi that has once been poured out of the container should not be returned to the container. This is to prevent the liquid sumi in the container from spoiling.

Liquid sumi made by Japanese companies hardly ever contains low-quality ingredients. However, attention should be paid to cheap imports. On the other hand, high-quality liquid sumi stands up to those made by grinding solid sumi. Therefore, there is a growing number of users among top-class calligraphers.

On surusumi

A desired sumi ink cannot be obtained solely by grinding sumi against a suzuri (ink stone). Various methods are used such as, grinding sumi with the tip of a finger to create fine particles to adjust the desired ink color. Furthermore, the amount of water and the quality of the water, such as whether the water is hard or soft, compatibility with the paper, temperature and humidity of the day when the sumi is used all affect the color of the sumi as well as how the sumi expands. The effect tends to appear more readily specially in light ink painting. Each calligrapher studies how to make his or her sumi (surusumijiru) according to their own taste.

Machines that grind sumi called sumi grinding machines are sold commercially. They are appreciated by people who use large amounts of sumi.

Special notes

Some people use the mouth to suck on the brush with sumi on it when cleaning, but it is necessary to be aware of the health hazards in doing this.

Animal glue made from pigs and cows can be a serious religious issue. Therefore, one should especially be careful when instructing foreigners to put the brush in the mouth.

[Original Japanese]