Antique Pottery and Porcelain of China

A Definition of Chinese Ceramics

Due to a wealth of different ceramics created throughout the ages, the line between porcelain and other types of pottery is often unclear in China itself, the origin of porcelain. The Chinese term (Ciqi) that actually means porcelain is often used indisciminately for both china porcelain and pottery items like earthenware, including for those that are really early predecessors of real porcelain.

Chinese ceramics mainly are separated into two groups, earthenware pottery and porcelain. The concept of stoneware appears to be of European origin and is not used with Chinese ceramics, normally. The concept of soft-paste porcelain is foreign to Chinese ceramics.

Below is a clear definition from a Chinese source to what should be considered porcelain and what is earthenware pottery among Chinese antique ceramics.

Needless to say that when speaking of Chinese ceramics the terms used for "porcelain" and "earthenware" are frequently used in a way that the border between the two is muddled.
White clay was used in antique pottery like the Tang Sancai wares, and the clay of real porcelain was frequently not white.
In China earthenware is often also called porcelain, especially when the earthenware body is glazed, or does have an underglaze blue decoration; this even if items do not fall within the category of porcelain proper according to the table below.

Glazed Ming storage jar

Tang Sancai or other early Sancai wares were often made with white clay, but they were fired at lower temperatures than normal porcelain. Therefore, it is doubtful whether they should fall into the porcelain or the earthenware category (see table below).


Some of the green/greenish glazed pottery wares (Celadon) are also frequently called porcelain in Chinese, though they are really glazed earthenware. Then there are the Longquan ceramics which are categorized as porcelain but actually have a light gray clay body - normally, that is. There are Longquan items with white clay body too. The different colors were usually caused by (1) the color of the locally mined clay and, (2) the degree to which the clay was refined (impurities removed). Iron content would make a clay gray.

Some collectors use a simple way of categorizing ceramics: any ceramic body of high density with a high ringing tone is classified as porcelain. However, this is a bit too simplified a definition, it seems.


Differences between earthenware and porcelain

Other Pottery
Porcelain
Material normal clay Kaolin (china clay)
Color red, brown, gray white
Firing temperature 600-800° 1200° or more
Properties relatively porous & soft non-porous, hard & strong
Tapping sound dull sound clear ring
Water absorbtion high very low or none
Body non-transparent semi-transparent
Characteristics low chemical & mechanical resistance high chemical & mechanical resistance

* This definition may differ in Europe due to the existence of "soft paste" porcelain, bone china and different clays prior to the discovery of Kaolin.


Ceramic separation by age, in China
Worth mentioning here is a separation of ceramics according to age. In China many collectors make a difference between so-called early or "ancient" ceramics and later or "antique" ceramics. Normally, ancient ceramics refers to those before and including the Song/Yuan dynasties. But, most collectors will include underglaze blue/underglaze red ceramics from the Yuan dynasty in the category of the later ceramics. The latter usually includes Ming and Qing dynasty, and early republic ceramics. Thus the Yuan dynasty ceramics are the limit for either, but it depends really on the type of porcelain. This all despite the proven existence of porcelain even earlier.

Addition:
Archaeologic prrof shows blue and white ceramics as early as the Song and Tang dynasties, whereas the blue pigment and manufactuing method may have been different. Most proof comes from shards as few complete items are extant.

The actual time of discovery/development of real porcelain is not quite clear, but Kaolin seems to have been in use at least since the Tang dynasty.

Experienced Chinese collectors often specialize in either the ancient ceramics or the later porcelain as mentioned above. They feel that the field of knowledge required in Chinese ceramics is much too broad to allow for expertise in all.

Separation according to 'plain' and 'decorated' ceramics
Sometimes ceramics are separated in yet another way, namely by periods of plain and decorated ceramics.
The time before the Ming dynasty is called the 'plain ceramics period', while the Ming and Qing dynasties and later is called the 'decorated ceramics period'.
Before the Ming dynasty the majority of ceramics had no color decoration painted either under or on top of the glaze, thus they are called 'plain'.



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