Friday, June 7, 2013

Clay - Yixing Purple Sand, Zisha, Zhu Ni and Duan Ni

Yixing clay is often used as an umbrella term to describe several distinct types of clay used to make stoneware.
Purple Sand clay is made from Yixing clay. 
This traditional style was commonly used to brew tea in China.
It dates back to the 15th century.
Archaeological excavations have revealed that as early as the Song Dynasty - 10th century, potters near Yixing were using local "zisha" clay to make utensils that could have functioned as teapots. 
The late Ming Dynasty author Zhou Gaoqi stated that during the reign of the Zhengde Emperor (1502–1521) a monk from Jinsha Temple - Golden Sand Temple in Yixing handcrafted a fine quality teapot from local clay. 
These fine quality teapots soon became popular among the scholarly class, and the fame of Yixing teapots began to spread.  

Yíxīng teapots are actually made in Dīngshān.
Also known as Dingshu, which falls within the administrative area of Yixing. 
Hundreds of teapot shops line the edges of the town's crowded streets and it is a popular tourist destination. 
 Dīngshān is home to dozens of ceramics factories, Yíxīng Zǐshā Factory Number 1, which opened in 1958, processes a large part of the clay used in the region, produces fine pottery ware, and has a large commercial showroom.  

  • Zisha 紫砂 or 紫泥 ; literally means purple sand/clay. This stoneware has a purple-red-brown color. Producing region for this clay is Jiangsu Yixing Zhao Zhuangshan, Huanglong mountain.
    Teapots made with this clay fire at approximately 1065~1700 degrees C. The contraction ratio for this clay is high and therefore fired under high temperatures. The clay is sentive and does not do well with larger wares. It has the tendency to crack, deform and sand partiicles fall out after firing. Working with the clay requires patience and great skill. Due to its high porosity the teapot made from this clay brews tea very well due to it excellent air convection. The best types of teas to brew in a Zisha clay teapot is the Tit Kuan Yin, Taiwan High Mountain, Oolong and Puer.

  • Cautionary Tale: On March 10,  2011 the Yixing Teapot Art Institute in China reported that there was a massive recall of Yixing Teapots because it was uncovered by a reporter that the manufacturer has deliberately use toxic coloring to achieve the Purple Clay clay. 
See Following: 
 Media exposure beauty purple pot purple clay liner is made ​​with the Land and, in order to make it close to purple in color, many manufacturers add iron Pink, manganese dioxide and other chemicals for dyeing, at the same time being there are nine positive brand exposure . A time to have purple pot shelves. May 26 afternoon, the reporter deliberately visited Jinan Suning, Gome, triple trading company, several large supermarkets and stores more information about the handling of purple pot. Jinan, the survey found that all of America, nine Yang Yixing pot can be fully refunded ( March 10, 2011 05:40:48 Source: Purple House Editor: Zi Yan)


  • Zhusha or Zhu Ni 朱砂 or 朱泥; literally means cinnabar sand/clay. It is a reddish brown stoneware with a very high iron content. The name only refers to the sometimes bright red hue of cinnabar 朱砂; pinyin: zhūshā. There are currently 10 mines still producing Zhu Ni clay. Due to the increasing demand for Yixing stoneware, Zhu Ni clay is now very limited  in quantities. Zhu Ni clay is not to be confused with Hong Ni (红泥, literally means red clay. This is another type of red clay. 

 Basic components in this clay include aluminum, calcium and quartz.
The most interesting component of Zhu Ni clay is that it contains high concentration of iron.
 The iron component in Zhu Ni clay is so high which is why Zhu Ni pots are usually red.
 The Zhu Ni teapots are small and thin.
 The pots have a shorter heat storage capacity. 
The heat within the pot will dissipate easily. 
Due to the clay, the body of the pot will interact and respond
 to the external environment and temperature.
This causes an organic response with the tea, which can and will yield a better aroma and fragrance. The tea will have a smooth flavor.
A Zhu Ni clay teapot requires frequent and consistent use.
The clay has a tendency to dry out and shrink when not used. 
When a Zhu Ni clay teapot is being used again after a long storage it is recommended to re-season the clay.
The pot will crack if hot water is poured directly into it.
The correct method is to cover the lid of the pot and allow warm water to wash down from the lid to the body of the pot. 
This will warm the pot and reduce the temperature between the pot and the boiled water.
 After repeating this process for one or two times, you will be able to put brew tea and pour the water directly into the pot. 
This will prevent the teapot from cracking since the pot has already been warmed up and can endure higher temperatures.

  • Duan Ni 鍛泥; literally means fortified clay. It is a type of stoneware that was formulated using various stones and minerals in addition to Zi Ni or Zhu Ni clay. This results in various textures and colors, ranging from beige, blue, and green (绿泥), to black.
Ben Shan Lu Ni is formed within the layers of the purple clay 
of the Huang Long Mountain rock formation.
 The ancient name is known as the Li Pi clay Pear Skin clay or the Dragon Tendons. 
This clay is scarce and rare. 
The difficulty in mining and sourcing the clay makes it scarce and rare.
 It is generally beige after firing. 
The combination of Ben Shan Lu Ni and purple clay is used to produce Duan Ni.
 This clay requires very high firing temperatures.
 It is a difficult process in comparison to the production of other types of clay teapots.

The base color of the Duan Ni is not pure. 
White and black particles are found and become integrated into the beige base color. 
There are usually more black particles.
These are particles are surrounded by the yellow and white particles in a granules form. 
These particles are is not very prominent.
The layering between the particles are not obvious. 
The overall color of the pot always appears beige.

Sesame Duan is completely opposite to Ben Shan Lu Ni in terms of layers.
 Its base color is partial white, slightly dull with black and reddish particles.
The lack of white particles and the contrast in color makes
these black and reddish particles quite prominent.
 When compared with Ben Shan Lu Ni clay it is as if having colored dots all over this thin layer of dull white chiffon clay.
 From the density of the dark particles, it is clear that
Sesame Duan have significantly larger black particle density.
The color of Sesame Duan is highlighted and the layer of it is much clearer.
 Although Sesame Duan also has white particles.
These particle numbers are small and visibility is low.
On the whole the color tone of Sesame Duan is cold and rigid.

The differences between the clays are even more obvious after using the pot for brewing tea for a period of time.
Ben Shan Lu Ni will show a greenish hue.
 The beige base color will become more intense, soft and moist like Jade.
In contrast, the red particles in Sesame Duan will become dark red.
If the pot is used to brew Puer Tea the patina will increase and intensify.
 Long term brewing with Pure turns the pot to grow in reddish color.
Ben Shan Lu Ni feels smooth before and even after brewing with tea.
 Sesame Duan in contrast will feel rough and grainy.
Iron concentrations within clay 
When the iron concentration within a clay is around 4% the color of the pot after it is made will be light yellow.
About  7% iron concentrations it is called Satin Mud in Chinese Duan Ni 缎泥 - this yields a yellow. Iron concentrations of 10% will showed a natural or light gray.
Iron concentrations of 13% will be brown or coffee.
The iron concentrations in clay that are from 14% to 18% are usually red.

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