Yixing Purple Clay Material---Duan Ni
What is Duan Ni?
Duan Ni, also known as “Tuán Ni,” is produced in the mining areas around Huanglong Mountain. “Duan Ni” is a general term encompassing several subtypes, such as Benshan Duan Ni, Golden Duan Ni, and Sesame Duan Ni. Among various clay materials, Duan Ni typically exhibits the most diverse color spectrum, ranging from golden hues to bluish-gray tones. This makes Duan Ni teapots visually distinguishable from those crafted with other clays.
Duan Ni is one of the symbiotic clay sources within purple clay deposits, coexisting with green clay and purple clay. Consequently, it possesses characteristics of both types. Typically found beneath the top layer of the deposit and above the purple clay layer, Duan Ni may also be intermixed within the purple clay strata. Its distribution may vary slightly depending on the specific mining area, site, and excavation location.
Why does Duan clay have high breathability?
The breathability of purple clay depends on two factors: “clay mesh size” and “crystallinity.” A higher mesh size indicates finer particles and lower breathability. Conversely, a lower mesh count indicates coarser particles and higher breathability. Red clays like Zhusha typically have higher mesh counts, resulting in a finer texture and lower breathability—ideal for enhancing fragrance. Purple clay and Duan clay, however, can be processed into lower-mesh teapot clay with more pronounced granularity. Though slightly rougher to the touch than red clay teapots, they offer superior air permeability.
The degree of crystallization in clay also affects breathability. Higher crystallization reduces breathability. Red clay exhibits the highest crystallization, followed by purple clay, with green clay and segmented clay having the lowest. Thus, under normal conditions, segmented clay teapots generally offer higher breathability than red or purple clay teapots.
Why do segmented clay teapots come in multiple colors?
Two primary factors account for the diverse hues of segment clay teapots: the specific segment clay variety and firing temperature. Due to symbiotic mineral deposits, iron content varies among different segment clays, resulting in color differences—potentially leaning yellow, green, or blue-green. Segment clay with higher iron content yields reddish hues when fired, while lower iron content produces yellowish or brownish tones.
Another factor is the wide range of firing temperatures Duan Ni clay can withstand, typically between 1170-1200 degrees Celsius. Different temperatures yield distinct colors: lower-fired Duan Ni teapots tend to be lighter in hue, while higher temperatures produce teapots with bluish or even grayish tones.
Is it true that Duan Ni teapots tend to “spit black”?
Some users have noticed that Duan Ni teapots tend to develop “black stains” over time, with dark spots or patches accumulating on the body or rim. This phenomenon often results from insufficient firing temperatures during production. Alternatively, it may stem from loose clay structure and porous walls, allowing tea residue to seep through pores and accumulate as grime.
In fact, red clay and purple clay teapots can also exhibit this “blackening” phenomenon. However, since these teapots have darker colors, the issue is less noticeable. Duan Ni teapots, with their lighter hues, make any blackened patches highly conspicuous once they form. Therefore, users should regularly clean their teapots to prevent black residue buildup. When brewing tea, opt for lighter-colored varieties like light-scented Tieguanyin or green tea to minimize the formation of noticeable dark tea stains.
