Since everyone understands the role and importance of a teapot for tea drinking, we should now consider the material of the teapot, which is the famous Yi Xing ore. When talking about Yi Xing ore, most of the information you will find online only talks about its porosity, with little additional information. So first of all, what about the porosity in Yi Xing Clay? Is it really a unique characteristic of Yi Xing Clay?
To answer this, we must first understand the term "double porosity." This term basically indicates chain structure between the granules and the natural structure of granules itself. Thanks to these two charateristics, Yi Xing clay allows air and some moisture to pass through from both inside and outside. But is Yi Xing clay the only kind of ore clay which has "double porosity"? Probably not! As we know, "double porosity" will allow the teapot to grow shinier as it absorbs oils and other elements from the brewed tea leaves, which is not unique to Yi Xing Clay alone. Clay such as Lin's Ceramics "Lao Yen Ni", as well as Nixing Clay (Guangxi) and Jian Shui Clay (Yunnan) will also develop the same patina as well after repeated usage. This means that "double porosity" is not a "patent" of Yi Xing Clay at all, but a commonly found "feature" among different clays. As a result, we conclude "double porosity" is a trait which although it improves the function of Yi Xing Clay, but is not unique to it.
So what is so magical about Yi Xing clay then?
Another tricky question! If we do not use the actual ore to demonstrate, it would be impossible to answer. Yi Xing clay, processed from Yi Xing ore, has some truly special characteristics that are hard to find in other types of clay. First of all, it is able to transform itself into many different colors after firing. Secondly, it is able to form an incredibly lustrous surface unlike any other clay, which we refer as "water color" (水色). This is the glossy feeling we would normally find on most Zhu Ni teapots, or Zi Ni teapots after the "feeding". Third, different types of Yi Xing clay will bear a different "tuning effect", which we covered in Part 1.
Now we are going to enter the most confusing part of the Yi Xing world - the clay, and the ore itself.
Yi Xing clay (or ore) can be divided into three basic categories - "Zi Sha (Purple Sand)," "Pearl Mud (Zhu Ni)", and "Group Mud (Duan Ni)" (Some people might use Green Mud instead of Group Mud, but since Duan Ni is a mix of Zi Sha and Green Mud, we will just use Duan Ni) and knowing some geological terminology as well. First of all, Yi Xing is a sedimentary geological environment that was form between 540 to 190.4 million years ago. From this environment we can find sedimentary rocks such as Argillaceous Siltstone , Silty Mudstone, and Clayey Mudstone.
From here we begin the exploration of Yi Xing ores, and the very basic concept we should realize about Zi Sha, Zhu Ni, and Duan Ni, is that there are a lot of subcategories under each of these main categories.
For Zi Sha, we will encounter different types such as "Pin Zi," "Tian Chin", "Qing Shui," and so on. As long as the original ores fit the geological classification as "Argillaceous Siltstone," these ores will be considered "Zi Sha" clay. This type of ore is very hard like a stone, It also has a rough texture when held in the hand. In short, Zi Sha ore is very "rocky" looking and feeling.
below - This is a "Tou Zao Qing" (頭糟青) and "Er Zao Qing" (二糟青) ore were mostly used as the material for "Pin Zi Ni" (拚紫泥) or "Qing Shui Ni" (清水泥). It is a very common material for Yi Xing teapots, making it a foundational ore, which supports the economy of Yi Xing production even today.
below - this is "Tou Zao Qing," which means "First Layer Green". It means that it is located at the top of the seam. The rock on the right is a "Er Zao Qing," which means "Second Layer Green". It literally means that it locates at the middle part of the seam.
below - This is one of the most famous ore among Zi Sha - the " Di Zao Qing." (底糟青) The name basically came from its location in the seam, which is the bottom. This ore is considered to be one of the best Zi Sha available on the market for teapot crafting due to its pure quality and delicate texture. It is a cliche, but still worth mentioning - "Di Zao Qing" is famous teapot master Jin Zou Gou's (顧景舟) favorite ore.
below - The ore on the right shows a more reddish color due to kiln firing. This is what the ore would become after the firing in the kiln at a temperature of 1180c. You might also notice the greenish little block on this ore, the true identity of it would be revealed in the later installment of our Yi Xing blog series.
below - This is the ore that started the modern Yi Xing craze - "Five Color Mud". It contains multiple types of ore, such as Zi Ni, Hong Ni (紅泥), and even Duan Ni, hence the name "Five Color". You can still find some ancient teapots that used this type of ore, since at that time there were no advanced modern techniques for separating the different clay types from the ore (as are available today)!
below - Let's have a closer look to see if you can find the "five colors" in it...
below - This last ore we are going to introduce is probably one of the most confusing ore in Yi Xing. This is a Hong Ni (紅泥). The name literally translated as "Red Mud" in Mandarin. As a result, the color after firing will have a red color. But it is not Zhu Ni, although some Zhu Ni will have the red color as well, the texture is very different from Hong Ni. We will demonstrate such difference in our next article.
below - As you can probably feel from the picture, Hong Ni ore has very much a rock-like quality, which makes this ore very different from any of the Zhu Ni ores we will see in the next article. The red ore on the right is the ore after kiln firing at a temperature of 1100c. It has a red-orange hue!
In conclusion, Zi Sha ore is a type of sedimentary rock that is called "Argillaceous Siltstone". As long as the rock fits the characteristics of such, it will be categorized under the Zi Sha category. We will further discuss the other differences it has from Zhu Ni in Part III.
The discussion of "Zhu Ni" will continue in-depth in Part III, which should be fascinating for thos people who are attracted to Zhu Ni's unique quality.