What is special about Yixing clay?
How can you tell your Yixing tea pot is authentic?
If the tea pot comes from Yixing, it doesn't feel sticky. The clay is pleasant to touch. Although the surface appears grainy, the clay feels smooth.
If the tea pot is made from clay produced elsewhere, it feels sticky, a bit like touching glass.
Many people say Yixing clay is special because of its high ferric content. This is only part of the explanation.
Other parts of China have clay with high ferric content too. But they lack the special qualities of Yixing. Other parts of China have purple clay too. They also lack the special qualities of Yixing.
Yixing clay is known as zisha, which means "purple sand", as supposed to purple clay. The secret of Yixing lies in the "sand". It contains quartz and mica, and other less well-known minerals.
Scientific studies have shown that purple sand has different molecular structure compared to other clay types.
Mass Production vs Handmade
The quality of your Yixing tea pot depend on the quality of the clay. It also depends on how the clay is processed.
As a rule of thumb, avoid factory-produced tea pots. They may be cheaper, but are made of lower quality clay.
Mass-produced tea pots use pre-defined moulds to shape the clay rather than using a potter's wheel. It was more common, but more potters have since switched to traditional methods.
When you touch, you can tell the quality. The clay surface is rougher.
Yixing tea pot is multi-colored, yet it is unglazed. The colors are entirely natural. It is also free of toxic materials such as lead, arsenic, cadmium, and other toxic materials.
Known as "five colored" clay, the three most important clay types are:
Red clay (also known as hongni or zhuni)
In addition, you have the the white clay, which is ivory or creamy yellow, and the yellow clay that is tangerine orange.
Why is the clay so versatile? This has to do with its high level ferric content. Depending on the type of clay, it can range from 2% to 8 %, and often higher. By applying different kind of firing technique, different effects can be created without the use of external glazing.