Newsletter 02-2015

Content

• White porcelain & white glazes

• Scrap book notes (hints and tips that do not warrant a web page or an article on their own)

Blanc-de-Chine is the name the west has given to white porcelain hundreds of years ago

The early Blanc-de-Chine porcelain was far from a pure white.
The best idea of what 'pure' means would be calling it snow white.

Early white porcelains were anything but snow white. It could be termed as milk white, ivory, etc. but it was not (emphasis) pure white.

Basically, monochrome white porcelain consists of white clay and white glaze. If the clay has an even slightly different color, like a tint of gray, brown or other, then the resulting glaze is reflecting this after firing with a different hue.

Early whites, like the white porcelain of Ding kiln, usually had a tint of yellow. Even the wares of Dehua kiln, which later became the best known representative of Blanc-de-Chine, had a yellowish hue in the Ming dynasty. Holding a slightly translucent piece against the sun shows often a faint reddish hue, however. Only in the late Qing dynasty did the Dehua white wares become almost pure white. That means, only then was the clay white enough that Dehua did become to represent Blanc-de-Chine (china white) in the very sense of the word. This is due to its clay. Unlike some other kilns, the clay mined in the area of the Dehua kiln is already very white at the source, the whiteness is not the result of purification of the kaolin clay.

The same that is said above is basically also true for the white base of underglaze blue and otherwise decorated wares.

These wares do not normally have a white glaze per se, but they appear white because after firing the white clay is visible as such through the translucent glaze. If the clay had a different color, the glaze appears darker, with a different shade of white. Thus again, the whiteness is dependent on the purity or whiteness of the clay.
Impurities within it, or mixing of kaolin clay with gray or other clay colors will result in a darker white. Really pure white glazes will hardly ever be found in porcelain items made before the end of the Qing dynasty. The only exception may be imperial porcelain, because the clay of those was subjected to a much longer refining process than the average clay used by private (minyao) kilns. More of the impurities were removed as a result of this preparative treatment of the clay. The object of the whole was removing as much iron or iron oxide content as possible, both from the clay as well as the glaze, as iron would result in a darker color.

The clay was usually purified over a period of one year (two years for imperial porcelain). This involved treading it by foot, beating it with hammer-like devices driven by a water wheel, fermentation, flushing away foreign matter, etc. until the clay was considered good for use. The clay was then shaped into bricks and stored for later use.

Only in the late Qing dynasty, approximately the very late Guangxu reign, would it have been possible to find a pure white porcelain. Before that, porcelain glazes would show one of several hues, like for example the one called "duck's egg" color by the Chinese.
Well ... I have had difficulties imagining THAT color at first, although I had already eaten duck eggs for years. :-)

The white glaze of the porcelain should usually have an ever so slight shade of blue, gray, yellow, green or even pink. If you are not aware of this, just take a sheet of white printer paper and hold it besides a piece of porcelain. You will see the difference!

I can definitely confirm that this is not just talking - I restore antiques and have to replicate glazes of porcelain. There is never any snow white glaze coming with any Chinese antique. Such a glaze is almost always a sign that a piece was made in the 20th century.

So what has this to do with you?

You can use this information directly to detect authenticity problems. In the world of fakes we live in nowadays, this information is one of the factors you should take into consideration when evaluating whether or not to buy an antique. Anything that has a snow white glaze is suspect - it is very likely either from very late in the Qing dynasty or later in the 20th century. And yes, all what is said regarding monochrome white glazed items above is also valid for blue and white porcelain, even if the glaze may have a different composition.

For example, if you see an early 19th or even 18th century underglaze blue decoration, but the item has a snow white glaze, no matter what, it is more likely a later imitation or fake than the genuine thing.