Yixing Clay: Duanni

by Patrick

Benshan lüni, benshan duanni, huangjin duan, other Yixing clays (zisha) that are light-colored or yellow-toned after firing fall under the umbrella category of “duanni” clay. Duanni is the third broad category of Yixing clays which include Zini (all purple Yixing clays) and hongni (red clay, which also includes zhuni).

 Although there are various subgroups in this category, they share a number of important features. The original ores (原矿yuan kuang) in this category tend to be light grey, greenish-grey, grey with red or brown spots, and are comparatively softer and crumbly. The percentage of iron oxide in duanni is lower at usually around 2% (and no greater than 4%), compared to zini at 7-8% and hongni at around 10%. Firing temperature for duanni is between 1117-1200°C.

Benshan lüni shipiao teapot by Lin Hanpeng and Chen Chunhong.

What are the differences between clays?
​​The broad category includes numerous clays, some with little visible differences, some quite different in color and feel. Some of the more popular varieties in the market include: Benshan lüni, benshan duanni, huangjin duan, and mo lüni
 
Benshan duanni 本山段泥
Benshan duanni originally referred to the duanni mined from Huang Long Mountain 黄龙山 in Yixing, but now it is also used to refer to duanni which has a light yellow tone, but which isn’t as light or soft as benshan lüni. Benshan duanni original ore contains both lüni and zini. It is darker than benshan lüni and often has a rougher or sandier texture.
 
Benshan lüni 本山绿泥
Benshan lüni ore contains only lüni. The original ore is greenish grey (lüni 绿泥 means “green clay”). It has a very low iron oxide content even for duanni. When fired it has a very soft pastel yellow tone.

Duanni ore on the left and a duanni teapot on the right.

Benshan lüni ore on the left and Benshan lüni teapot on the right.

​Huangjin duan 黄金段
This clay is called huangjin 黄金or gold duan because it has a golden tone after firing. Huangjin duan is a thin layer of duanni that is found just below the surface of the mountain. It is quite rare compared to other duanni ores.

Huangjin duan teapot.

​Mo lüni 墨绿泥
Mo lüni is a fairly common clay in the market. Its name translates to “green ink clay” because of its dark green appearance after being fired. This clay is in fact a mixture of clays and one or more colouring agents. There is no original ore that will turn green after being fired. This clay usually consists of the clays benshan lüni, bai duan, as well as the colouring agents chromium oxide and/or cobaltous oxide. True mo lüni clay following the above formula is safe to use. There are many fake green teapots that use other chemicals (some dangerous) to replicate the color of this clay. We advise caution when purchasing a green Yixing teapot.

Mo lüni teapot.

What is duanni good for?
As always, we advise trying your teapot with different teas to see which combination you prefer. In general, duanni teapots are more porous/absorbent than other Yixing clays, and tend to retain heat longer. They are good for teas that like more heat for a longer period (like shu puer) and they are good for absorbing the unpleasant flavours of some teas (hints of smoke). We like them for shu puer, very strong semi-aged sheng puer, and some high roast wuyi wulong teas.