Proto-porcelain

There is ongoing discussion about whether "proto-porcelain" is a good descriptor, but it remains in use due to its utility in tracing the technological progression of Chinese ceramics. Some are fine with broader terms like "stoneware" or "early porcelain," depending on their focus, but in practical use the term Proto-porcelain despite its shortcomings describe a range of well recognized wares, usually dressed in a green ash glaze.

Proto-porcelain wares were first produced by Zhejiang potters as early as the Shang dynasty (1600–1046 BCE), with more refined production occurring in the later Zhou Dynasty (1046–256 BCE). One of the primary differences between proto-porcelain and traditional low-fired pottery is its lower water absorption, making it more versatile and durable than traditional low-fired pottery. The ability to fire ceramics at higher temperatures, along with innovations in glazing, was enabled by parallel advances in metallurgical techniques and kiln technology.

The term "Proto-porcelain" is referring to early Chinese ceramics that have some, but not all, of the properties of true porcelain. These ceramics were fired at much higher temperatures (typically between 1200–1300°C) compared to traditional low-fired pottery (fired below 1000°C). The high firing temperature caused the clay to vitrify, creating a denser, more compact body with much lower porosity. This low water absorption made the vessels more durable and capable of holding liquids without seepage, unlike low-fired pottery, which could absorb water and degrade over time.

With lower porosity, proto-porcelain was not just stronger but also more hygienic, as it was less prone to harboring bacteria and stains. This opened up new uses in both daily life and ceremonial contexts, including storage jars, vessels for liquids, and items for burial. Its increased durability made it a more practical material for functional ware, such as cooking vessels, storage containers, and transportation jars, where exposure to moisture was frequent.

Some scholars argue that these wares should simply be classified as stoneware but while all proto-porcelain is a form of stoneware, not all stoneware is proto-porcelain. Proto-porcelain specifically refers to en early type of high fired ceramics that are on the path toward true porcelain in terms of material composition, and firing technique.

Some scholars prefer the term "early porcelain" to describe these wares, especially as proto-porcelain exhibits many of the characteristics of later true porcelain, including the use of kaolin clay and high firing temperatures. The use of "proto-porcelain" suggests an evolutionary process, with proto-porcelain representing an intermediate step between stoneware and the fully developed porcelain seen in later dynasties. However, the line between early porcelain and proto-porcelain is blurry.

In Chinese scholarship, these early high-fired ceramics are sometimes referred to as "yu tao" (釉陶) or "ci" (瓷), both of which can be translated as "glazed pottery" or "ceramics." which are less specific than "proto-porcelain".

Some scholars prefer to describe these wares as Han stoneware or Zhou glazed wares, based on their time period and technical characteristics.

Despite these debates, "proto-porcelain" remains the most commonly used term in Western scholarship, primarily because it captures the idea of an evolutionary process toward the development of true porcelain. The term is useful for distinguishing these early ceramics from both coarse stoneware and the fine, fully developed porcelain of later periods.

Where:

The production of proto-porcelain originated primarily in southern China, particularly in the regions of Zhejiang and Jiangxi provinces. These areas were rich in the natural resources needed for proto-porcelain production, including fine clay and wood ash, which were essential for creating the early glazes. The kilns in these regions, particularly the Shanglinhu kiln complex in Zhejiang, are known for producing some of the earliest examples of this type of ware.

When:

The shapes and forms of these vessels, like many ceramic wares of ancient China, were imitating their bronze counterparts. The production and quality of proto-porcelain ware was at its peak during the Spring & Autumn Era (770-476 BC) and Warring States (475-221 BC), basically Eastern Zhou (770 BC-256 BC).

Shang Dynasty (1600–1046 BCE): Early forms of high-fired ceramics, which could be considered proto-porcelain, began to appear. These ceramics were stoneware, fired at higher temperatures than ordinary pottery, making them harder and more durable.

Zhou Dynasty (1046–256 BCE): This period saw further refinement in the technology and aesthetics of proto-porcelain. Glazing techniques, including the use of wood ash as a glaze component, developed during this time, laying the groundwork for what would later become true porcelain.

Han Dynasty (206 BCE–220 CE): By this time, proto-porcelain production had become more widespread. The ash-glazing technique, in particular, was refined, resulting in smoother, more uniform glazes. These early glazes were usually greenish due to the presence of iron in the wood ash, which would oxidize during firing.

Yuan Dynasty (1279–1368 CE): This is the period when true porcelain as we know it emerged. The Mongol Empire’s expansive trade routes helped facilitate the flow of cobalt, which was a rare and expensive material while Jingdezhen became a major production center for this new style of porcelain that added cobalt blue decoration on top of a true white porcelain body.