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Relationship between Celadon, Qingbai and White wares

 

Iron oxide is the most important colourant for glaze in ancient Chinese ceramics production.  The earliest glazed ceramics termed proto porcelain green ware in China has iron oxide as the colourant.  Its discovery as a colourant is most probably accidental as it is present in the raw materials such as rock/clay and the plant ashes used by the Chinese potters.  The final colour tone of the glaze depends on a few important factors:

a)  the amount of iron oxide in the glaze

b)  the state of firing process, ie whether it is oxidation or reduction.  Oxidation is the natural state during firing.  To achieve a reduction atmosphere, the amount of air entering the kiln is reduced or by over-stoking the firebox with fuel.  Under oxidation, the iron oxide in the glaze is converted to ferric oxide (red iron oxide).  For ferric oxide of about 0.5 - 2%, it will give a ivory to straw tone, greater than 2-3%,  a yellow tone, 3-4%  a amber tone, 3-4% ,4-5% a amber-brown tone and 6-8% different degree of black.  In state of reduction, the iron oxide is converted into ferrous oxide (black iron oxide).   For ferrous oxide of 0.5-1%, it gives a icy-blue tone (as typical in the Qingbai wares) and for 4-8% a shinny black.

c) the presence of titania.  When small amount of titania (0.2 to 0.5%) is present with ferrous oxide in the glaze during reduction state of firing , a varying range of green, grey-green, green-brown and olive-green is produced.  This type of wares is termed celadon or greenware, the most famous being Yue , Longquan and Yaozhou wares.

 

Chinese celadon wares had been produced in China since the Shang Dynasty.  With above background information, it would not be difficult to understand why celadon has such a wide varying degree of colour tone.  However, sometime celadon could display a light bluish tone especially if the iron oxide content is lower and titania presence is low.   This is especially so for those produced during the early Southern Song and earlier which used a lime glaze formula.  Such glaze tends to be thinly applied on the ware and is more transparent.   They look very similar to Qingbai ware of the same period which also has a lime glaze formula.  As we know the typical Qingbai ware as represented by those from Hutian has a icy bluish tone.  Essentially the only difference would be that Qingbai ware tends to be more thinly potted and the body has a more whitish translucent paste.  In comparison, the typical  celadon ware usually has a more greyish paste and more thickly potted.  The same problem of terminology arises for those Qingbai wares which has a yellowish tone or more greenish blue tone, as such colour tone is also found in wares usually termed celadon especially those imitation of the famous lonquan wares made in Fujian.  A good example is the below bowl on the left which has a light bluish tone (The one on the right is a typical Longquan celadon bowl). This bowl is thickly potted and has a more greyish paste.  A similar bowl was termed Qingbai ware by a well-known expert on chinese ceramics in her book on chinese ceramics.  Such bowls were either produced in Zhejiang or Northern Fujian region during the early Southern Song period and would typically be termed green wares by ceramics experts in China.

The above photo displays group of celadon and qingbai.  Group enclosed in green is typical celadon with the thicker lime akaline glaze formula.  Group enclosed in white is typcial Qingbai.  Those enclosed within yellow line are Fujian celadon.  Some of them in this group shows Qingbai colour tone (this group is enclosed with red line).  From colour tone perspective, it is qingbai.  However, why are they labelled as Fujian celadon.  What is the reason?  The argument  is that they are more thickly potted, has a more grayish paste and similar types with more typical celadon colour tone are produced in this group.  Hence, the classification is based on features which not just consider colour tone but also other features more closely associated with this type of bowls.  To a certain extend, there is some elements of subjectivity.  If we look at it objectively, certain questions remains.  Is it  the potter intention to produce a more greenish celadon glaze as more typical found but due to uncontrollable firing condition or problem of laze content, a more qingbai colour materialised instead?.  Or could it be the  potter's actual intention to produce a more Qingbai tone?.  We do not have the answer as insufficient information could be gathered from the archaeologyical excavations.  

Personally, I don't think neither classification is wrong.  It depends on the angle we look at it and give the basis of our classification.  From the point of view of colour tone, it is indeed more akin to qingbai.  For those who termed it celadon, it is mainly because of other considerations  such as the more thick potting, more greyish paste and the knowledge that similar bowls were produced in kilns that produced typical celadon ware.  The term Qingbai and green ware (or celadon)  were coined most probably to describe the colour tone.  Such description will at times give raise to problem as certain colour range are found in both the so called celadon and qingbai ware.  This is especially so for those imitation of Hutian Qingbai or Longquan celadon wares which were produced in other regions such as Fujian.  The colour tone and paste usually differs for a certain extend from the typical Celadon and qingbai wares.  We should not be confused and troubled by the constraint of the  terminology.  What is important is understanding the history, the production processes of such wares and the scientific explanation for the colour as we see it.

 

Classification of some white ware also posed a similar problem.  Many has a very light bluish tone where the glaze pooled.  True white ware is actually transparent due to the absence of the colourant iron.  But in many instance a small amount of iron oxide is present in white ware.   Whether terming it Qingbai or white ware is thus subjective depending on its impression to the viewer.  To me, there is no right or wrong answer.

 

For those who are interested in understanding Cinese ancient ceramics from a scientific perspective, he/she should get a copy of the book "Chinese Glazes" by Nigel Wood. The above short explanation is based on information in the chapter "Iron in glazes" in the book.  For those who understand Chinese, the book "中国古陶瓷的科学" by Prof. 张福康 would be an additional important reference .

 

 

By : NK Koh (29 Aug 2009) Updated 27 Nov 2010

 

 

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