An interlayer of a mine layer, the ore body is thin-layered and lenticular. The thickness of the ore layer is generally about tens of centimeters to one meter. The color of the raw ore is purple, reddish purple with light green spots. The color after burning is purple, purple-brown, purple-black. The main component of purple clay is hydromica, and it contains unequal amounts of kaolin, quartz, mica chips and iron. It has good plasticity, high strength and low drying shrinkage.
Aged Purple Clay
The so-called "old" refers to the "heavy sandy" mineral material, which has a lot of quartz particles. It is difficult for pot formation and has a high sintering temperature.
It also refers to the aging time of the mud, and the long aging period > 3 years is called old mud. The plasticity of the old clay is relatively high, the color is relatively mild after firing. The stale period of the mud is, in a sense, the longer the better, but the mud with too long stale period needs to be tempered again before making the pot.
Staleness is not simply a "long-term storage". Instead, the wet mud is placed in a kiln or pottery jar that is impermeable to sunlight and air. A certain temperature and humidity must be controlled to facilitate the production and development of humic acid.
The pot made of "aged purple clay" is purple-brown which is mature, dignified and solemn. That makes it the best choice for pot lovers who love the simplicity of old pots. Different firing temperature is required depending on the the proportions of various metal oxides in the old purple clay which gives out different purple colors.
Celestial Clay (Tianqingni Ni)
It is originally produced in the Huanglong Mountain Big Reservoir, first discovered and produced in the middle of the Qing Dynasty and is famous for its scarcity. It is the top clay type among purple clay group. After highfired , the pot color is deep reddish purple.
is also called clear water sand, which is a more common among other purple clay; high quality clear clay is scarce and expensive, the inferior is of abundance but cheap. It is one of the most popular clay used by ancient potters.
Its optimum kiln heating temperature is 1160 degrees. Shrinkage ratio: about 12%. It is easy to use, good affinity, simple temperature control, easy in pot caring, and it will become more elegant reddish color.
It is located at the bottom of the purple clay layer, the mineral material is generally purple-brown compact, with bluish green spots. It becomes pink color when the firing temperature is between 1160-1180 degrees Cel. At the temperature between 1190-1200 degrees Cel. , it becomes dark purple. In Gulong kiln (Aged Dragon Kiln古龍窯), it can become grey, black, and greenish black.