Does Jianzhan Belong To Pottery Or Porcelain

Ceramic, Pottery, Porcelain – as someone who enjoys Jianzhan teacups, you must come across these terms frequently. Have you ever wondered about their differences? Is Jianzhan made of pottery or porcelain?

From a historical perspective, pottery predates porcelain to the extent that many people influenced by pottery cannot correctly distinguish the characteristics of various types of clay. Combined with the innovative ceramic firing techniques of modern times, this often leads to confusion.

1. Clear Definitions:

1) Ceramics is a broad term for various hard products made from non-metallic materials.

2) Porcelain: Porcelain is a high-quality type of ceramic. It is usually made from white or near-white clay. Porcelain has a high density and low water absorption.

3) Pottery: Pottery refers to ceramic products made from clay. Pottery typically has lower density and higher water absorption compared to porcelain.

2. Differences between Pottery and Porcelain:

1) Different Raw Materials:

Pottery is made from general clay. When fired at temperatures between 800-900°C, it becomes pottery. If the temperature reaches 1200°C, it will not become porcelain but melt into glass.

Porcelain, on the other hand, is made from kaolin clay. When fired at temperatures around 1300°C, porcelain is obtained.

2) Difference in Iron Content:

Pottery generally has an iron content of over 3%, while porcelain usually has an iron content below 3%.

3) Different Firing Temperatures:

The firing temperature for pottery is generally lower than that of porcelain, ranging from below 800°C to around 1100°C.

Porcelain requires higher firing temperatures, mostly above 1200°C; some can reach around 1400°C.

4) Difference in Glazing:

Pottery is often left unglazed or glazed with low-temperature glazes that melt at lower firing temperatures.

Porcelain is commonly glazed using both low-temperature and high-temperature glazes.

5) Difference in Hardness:

Pottery is relatively rough and has a higher water absorption rate. It has a poorer hardness with lower firing temperatures, and some can even be scratched with a steel knife.

Fired at high temperatures, porcelain is sturdy, dense, and non-absorbent. When tapped, it produces a metallic sound.

3. Jianzhan Teacups:

1) Glaze: Jianzhan teacups have over 70% of their surface covered in black high-temperature glaze. In this aspect, they are closer to porcelain.

2) Firing Temperature: Jianzhan teacups require a kiln temperature of 1300℃ to be fired and finished, making them closer to porcelain.

3) Iron Content: Jianzhan teacups have an iron content of 8%, which aligns more with the characteristics of pottery.

4) Hardness and Water Absorption: Jianzhan teacups are sturdy, dense, and non-absorbent, which aligns with the characteristics of porcelain.

4. Controversy:

Professor Liu Tangshen from Fudan University believes that Jianzhan teacups, based on certain features, actually fall into a category between pottery and porcelain called Stoneware (炻器).

The key factor is the water absorption rate, as one characteristic of porcelain is extremely low water absorption (modern white porcelain has an absorption rate below 0.5%). In contrast, Jianzhan teacups have an absorption rate of less than or equal to 5%. Therefore, according to ceramic standards, they are closer to Stoneware (炻器).

5. Conclusion:

The widely accepted view now is that Jianzhan teacups belong to black porcelain, based on the following aspects:

1) Glaze: Jianzhan teacups are glazed with black high-temperature glaze, resembling porcelain.
2) Firing Method: Currently, Jianzhan teacups are fired at temperatures above 1300°C. When a drop of water is placed on the unglazed bottom, it shows no signs of absorption, indicating good porcelainization.
3) Microstructure: Pottery and porcelain have distinct differences in appearance and microstructure. Jianzhan teacups have a high iron content in their glaze and belong to a type of lime glaze (iron-calcium crystal glaze).

A key criterion for identifying porcelain is the silica content ratio, and the silica content ratio of Jianzhan teacups is closer to porcelain.
4) Firing Difficulty: Firing Jianzhan teacups is constrained by multiple factors, making them one of the most challenging monochromatic porcelain to fire, with low yield rates.