Zhu Ni (red clay) is very precious and in the past was valued at over 50 times the price of regular purple clay, being sold by weight. However, Zhu Ni has limited sources and is challenging to mine.

Zhu Ni is not a single type of clay. Some people believe that only so-called “wrinkled” or “pear skin” clays are Zhu Ni and are considered high-quality Zhu Ni. Such an understanding is extremely narrow and superficial, mainly due to a lack of knowledge about Zhu Ni or being misled by some rumors, causing many enthusiasts of red clay to go astray. Zhu Ni, Dahongpao (generally darker than Zhu Ni Teapots, often purplish red or rose red), and Xiaohongni all belong to the red clay category.

In Yixing, there is more than one source of Zhu Ni, for example, specific mines include: Huanglong Mountain Zhu Ni, Qinglong Mountain Zhu Ni, Zhaozhuang Mountain Zhu Ni, Xiangya Mountain Zhu Ni, Lanshan Zhu Ni, Xiaomeikiln Zhu Ni, Wushan Old Rockmouth Zhu Ni, Xiangshan Zhu Ni, etc. Within these areas, different sub-layers and varieties of clay can be found. Different mines have different mineral compositions, resulting in distinct characteristics when fired into teapots.

A comparison between Xiaomeikiln Zhu Ni, Dahongpao, and Zhaozhuang Zhu Ni

The Essential Differences Between Zhu Ni and Red Clay

1. The original ores are different: Red clay is ordinary clay from the “Five-Colored Earth,” while the original ore of Zhu Ni is Shihuangshi (stone yellow stone).

2. The shrinkage ratios are different: Red clay's shrinkage ratio is around 14%, while Zhu Ni's shrinkage ratio is around 30%.

3. The firing temperatures are different: Red clay is fired at 1100 degrees Celsius, while Zhu Ni is fired at 1080 degrees Celsius.

4. The colors and textures are different: Red clay appears bright and glossy with a reddish hue slightly tinged with orange, while Zhu Ni appears a deep red with a slight orange glow, having a moist and transparent texture.

5. The forming processes are different: Red clay is relatively easy to form and can be made into both large and small teapots, while Zhu Ni is difficult to form, making it unsuitable for large Teapot sizes but ideal for small, lively ones.

6. The sounds produced by tapping are different: Zhu Ni, with a higher degree of vitrification, produces a sharp metallic sound; red clay, with a lower degree of vitrification, produces a deeper sound reminiscent of earthenware.

The Main Characteristics of “Zhu Ni”:

High crystallization, the cross-section of the clay approaches the quality of porcelain. When the lid is lifted from the body of the pot, a metallic sound can be heard, and tapping produces a crisp sound with resonant overtones. The color resembles an orange; before firing, the clay is orange-yellow, and after firing, it is red with a hint of orange. Pouring hot water over a Zhu Ni teapot immediately reveals a vibrant red color, with purple light floating in the mist. After seasoning and patina development, the red color becomes more stable. It has a high shrinkage rate and is difficult to shape, often resulting in deformation during firing; throughout history, it has mostly been used for smaller pieces. It has a high iron content, and if fired at too high a temperature, iron spots may appear.

Is the Saying “Nine Out of Ten Zhu Ni Pieces Have Wrinkles” Correct?

Although Zhu Ni teapots have greater vertical shrinkage than lateral shrinkage, the phrase “no Zhu Ni, no wrinkles” does not accurately describe all cases. Many extant Zhu Ni works do not have wrinkles. With careful selection of the clay, understanding its properties, and proper processing, Zhu Ni teapots can be made without wrinkles.

Why Is Water Not Easily Dried in a Zhu Ni Teapot?

Zhu Ni has a high density, making it most suitable for brewing lightly fermented teas like Tieguanyin, which release their aroma quickly and with great intensity. The fact that water is not easily dried in a Zhu Ni teapot does not indicate a problem with the clay; rather, it is a characteristic of the material. Teapots made from other types of clay, such as Zini (purple clay) or Luni (green clay), have a lower density and thus dry out residual water more quickly.