One category consists of inferior quality pots with no collection value, and the other category consists of Yixing purple clay pots with collection value.
The raw material for inferior quality pots is often low-grade materials such as casserole clay or vase clay. Their colors are oily and stiff, and when broken, it can be clearly seen that the color of the inner and outer layers are different. The price of these pots is usually between a few yuan to dozens of yuan, and they basically have no collection value. The real Yixing purple clay pot uses purple clay produced in Dingshu Town, Yixing. Purple clay is a unique raw material of Yixing, which has the necessary chemical composition and mineral composition required for pottery making. Under microscopic observation, it was found that the main minerals in purple clay are quartz, clay, mica, and hematite. The particle composition of these minerals gives the purple clay good plasticity, high green body strength, and low shrinkage during drying. Since the body of the purple clay pot is not glazed, it still has a large water absorption rate and porosity after firing. According to measurements, the water absorption rate of the purple clay teapot is between 1.6% and 7.05%. Therefore, the finished product has good gas adsorption properties and breathability, making it suitable for brewing tea with excellent color, aroma, and taste.
Methods for identifying pure purple clay:
1. Look at the color: The color of pure purple clay, whether it's purple, yellow, red, or any color in between, should have a jade-like charm. Its luster is a dull shine, like being oiled, becoming smoother with more polishing. It cannot be waxed or polished, but instead, one can refer to the material effect of old jade. The rarer the material, the more valuable it is, because the resources are limited.
2. Listen to the sound: A purple clay pot is the finest among ceramics, so its sound is the sound of ceramics. After brewing tea, the sound is rough, hoarse, and deep, unlike the crisp sound of metal or porcelain. A hoarse sound indicates good breathability of the material, internal non-crystallization, and the ability to retain the aroma of tea without changing its flavor easily.
3. Feel: The feel of a purple clay pot should be smooth, round, and comfortable, with particles that are very round. The appropriate size of purple clay particles is generally between 32 and 60 mesh. The feel of sand powder processed by traditional manual methods and stone grinding is different from that processed by machines.
4. Pot nurturing effect: With a good purple clay pot, after brewing tea slightly and then wiping dry with a cloth, a matte finish with heavy oiliness can be observed. The longer the pot is nurtured over time, the deeper and more ancient the color becomes, until the pot develops a sense of spirit and connects with human emotions.