Wednesday, July 14, 2010

Two beautiful blue bowls

A relative went down to the Palo Alto Clay and Glass Fair during the weekend, and came back with some bowls by Dick Lumaghi that appear to be pale Jun glazes, but no copper.
Or possibly rutile (segar) blues.
But I'm just guessing.

For those not in the know, Jun (鈞) glazes consist of at least three or four color influences.

[Jun glazes are so called after Jun-yao (鈞窯) ware, a type of celadon made during Sung, Chin, Yuan, and early Ming. The effects of the glaze are achieved by planned variance in firing temperature.]

This is caused by a separation in the molten glaze that can only occur at temperatures below 1200 and while the glaze is viscous. So it cannot occur in most kilns.. The kilns in China that produce Jun ware are heated up over a period of days, then gradually cooled down over several more days, allowing the opalescence to occur in the glaze. This can only result if the temperature is right for a long time.

These are caused by the inclusion of Wollastonite. The melting point is 1,540˚C.
Wollastonite is an impure limestone naturally compressed in the presence of silica-bearing fluids. It often contains traces of irons, magnesium, and manganese. Most Wollastonite comes from China, although it is also mined in Gouverneur, New York.
In ceramic, the crystalline structure of the material causes a streak effect between glassy and pearlescent.

Blue blue green
Like Celadon, the glaze material contains iron, which gives it a blue or blue-green effect. Iron oxide, reduction firing.

Additionally, many Jun glazes ALSO contain some copper, which results in purple hues.

What makes me think that the glazes on Dick Lumaghi's pieces is Jun style is that there is more body to the bowls. These do not feel as fine-paste porcelain, but more robust. Very much like high-fired stoneware. They have a well-chosen heft to them.

They are delightful "plant your face here and eat" bowls.
Perfect for chopstick meals.


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