01. Tea Mountain: purple clay Teapots have good breathability. The tea stains that adhere to the pot over long-term use are usually referred to as a tea mountain.
02. Aging: Also known as “nourishing the soil,” this is the final processing step for purple clay. Well-mixed and refined clay is placed in Ceramic vats and stored in a damp, shady place to ferment and age.
03. Aging Period: This refers to the time from when the well-mixed and refined clay is placed in a damp, shady spot to start aging. Like fine wine aged in underground cellars, the longer the aging period, the smoother and more elegant the resulting Teapot will be. The minimum aging period should be at least three months.
04. Patina: After years of use, a natural and unique luster forms on the surface of the teapot. This luster is restrained and deep.
05. Sun Lines: In the bottom center of a purple clay teapot, there are radiating lines like sunbeams in the clay, which are called “sun lines.”
06. Original Purple Clay Mine: Many purple clay artisans exaggerate by claiming they use “original purple clay mine” for their works. In fact, purple clay is broken down into mud, and the raw material commonly used for making purple clay teapots is processed from purple clay ore, often referred to as “refined clay.”
07. Weathering: After being extracted, the ore is left exposed to the elements, subjected to sunlight, rain, wind, extreme heat, and cold, causing it to break down from dense blocks into loose granules. The texture changes from hard rock to soft earth, a process known as “weathering.”
08. Mesh Size of Clay: After extraction, the purple clay ore undergoes weathering, removal of impurities, and crushing. The coarseness or fineness of the clay after sifting is referred to as the mesh size. This process is also known as sieving. There is a history behind mesh sizes: during the mid-Song Dynasty, the mesh size was 26-35; in the early Qing Dynasty, it was 35; and in the mid-Qing Dynasty, it was 55-60. (Before 1957, manual refining methods were used, leading to lower mesh sizes, better permeability, coarser particles, and stronger texture. This is one of the criteria for identifying old teapots. Follow WeChat ID ee2266 to learn more about purple clay knowledge.) Mechanical sieving began in 1958 with a stable mesh size around 60. Since 1959, Raymond grinders have been commonly used, controlling the mesh size by wind power, capable of achieving mesh sizes as high as 140-180. For modern purple clay teapots, different refining methods are used, generally controlling the mesh size around 60. Using 60 as the baseline, the higher the mesh number, the finer the clay; conversely, the lower the number, the coarser the clay.
Source: Chinese Tea culture Knowledge