The double air hole structure of celadon teapot is mysterious.

When talking about the special features of purple clay mud, a word comes up to mind - double-hole pore structure. Today I'll be explaining in detail the benefits of this dual-pore structure.

First of all, the two pore refers to the various minerals combined with purple clay mud forming pores and internal pores of small groups of clay. The production of dual pore is caused by the inherent structure of purple clay itself as well as the different shrinkage rates of various minerals in the firing process of purple sand pot.

The first kind of pore is a chain-like pore generally formed by the contact faces between different minerals. Some of these pores are connected and some are closed.

The second type of pore is a small pore in silt aggregate, which is an internal closed pore and an open pore on the surface of the silt aggregate.

Purple clay's "double-pore structure," is closely related to its quartz component. Purple clay's "purple" refers to color; purple clay's "sand", refers to properties.

Sand, has two meanings: one for single crystals of pure quartz grain, one for complex aggregates of quartz. We usually refer to purple sand that means the latter meaning.

Yixing teapot broke, you can see its fracture section and clearly judge its special structure. During firing, the carbonate ions in the clay first decompose, releasing carbon monoxide and carbon dioxide gas to form bubbles.

Bubbles in the soil are connected and closed, forming a dense "chain-like pore groups", linked to open; bubbles gathered on quartz and silicate particles will block between each particle, make originally existing voids not interconnected, prevent and lead to close. Open airways and closed airways coexist, called "intervort structure," colloquially referred to as "double pores."

Purple clay teapot's double-porous structure

Observe the cross-section of a fired purple sand teapot: The open pore interspaces between masses, large gaps, allowing gas to enter and exit; the closed pore interspaces within the masses are small, preventing water from entering.

Black Mud Heart Stone Basin

The clay without purple sand, has no quartz grains and salt lump. Without firing, they are all open pore; will seep water spitting black; after firing, completely get rid of pores.

Zhu Ni Qi Duan

Because of the surface tension of tea, it can't get out through these pores on the surface. At the same time because molecules of gas are much smaller than water molecule, the steam of water can still go out from these pores. This is what people often say - breathable but impermeable to water.

Purple clay censer

As the steam of tea water passes through the tiny holes in Yixing teapot, some are trapped in the irregularities of the holes and remain there after evaporation, allowing the flavor to be stored inside. This is why a purple sand teapot can retain tea scent.