Chuns

GLAZE OF THE WEEK 4

TRANSPARENTS: CHUN IS FUN ( SO IS NELSON’S TRANSPARENT)]

  • Clear, stable, Cone 10 glazeS

  • In reduction, soft celadon green on white clay

  • Color can vary from clear>gray>blue>opalescent>to light green

  • Combines well with Royal Blue and Oribe glazes, and ceramic stains v When thin, Chun makes an excellent glaze over colored underglazes.

Chun is a Cone 10 glaze originally from the Sung Dynasty in China, greatly admired and copied throughout the world. Nelson’s Transparent is very similar, but has a small amount of iron in the formula. They are both clear glazes like the celadons which react to produce tints of color when there are small amounts of iron oxide present in the glaze or the clay body. Depending upon the proportions of iron oxide, phosphates, limestone and quartz, transpaent glazes can be clear, white, opalescent due to microscopic bubbles which form as the glaze matures in firing, light blue, gray, or delicate green. Firing conditions influence HPG Transparents. In oxidation Chun is clear, in reduction it can have a faint celadon green tinge. When thin, HPG Chun is always colorless and smooth. Rarely it can be seen to have a fine craze. Nelson’s Transparent is clear with a celadon green tinge in reduction; more blue/gray in oxidation. It is the characteristic crystalline structure which makes celadon glazes.

Designs using ceramic stains are shown to good advantage with transparents, as often demonstrated by Esther Nowell with her blue patterns, Judy Kawabata’s colored underglazes, Kazuyo Sato’s flowery colors and Marie Kodama’s finely drawn patterns.

Chun and Nelson’s Transparent are stable glazes, do not run in firing. unless too thick with added glazes. They combines well with accents of other glazes. Favorites are small amounts of Royal Blue and Oribe green. In reduction, the red underglazes come out well enough. Etsuko green is “fake celadon green” (see Ch 7) using a “pinch” of chromium stain (0.125 % seems to work). A 50-50 proportion of Chun and Nelson’s Transparent is a good mixture when using a colorant like chromium to maintiain clarity. Sky Blue Chun is a light clear blue with cobalt. A recent experiment attempting to get a blue-green (soft aqua) chun by adding chromium and cobalt together ended up as a shiny purple glaze. One never knows. A new experiment will try for amber celadon.

Two new Chuns have been tested with satin finishes, not transparent.
The recipes are made for Cone 9-10, therefore pots with these glazes would best be placed in the cooler part of the kiln which durrently is at the top, but variable. Reduction is required for color development. Blue Chun is expected to have a clear medium blue color. The current batch of Plum Chun produces a rasberry wine color with beige sometimes. The presence of a component called Gerstley

Borate could give these glazes a flowing iridescence in some places on the piece.

These new Chuns may run, so keep well off the bottom of the pot. They work best on porcelain or white clay in reduction, but turn rather tan on dark clay. These glazes seem to be rather finicky in our firings, but may be worth the risk.

Another transparent glaze is McKenzie Celadon which is a clear olive green, or khaki, on porcelain, and on darker clay it will appear the same except for iron freckling. [see Ch 8]

The recipes for these new Chuns have only a tiny amount of cobalt blue or copper green, and certainly no purple. Where do the colors come from? Interactions of minerals and iron create minute crystals which diffract light in certain ways, giving characteristic colors if reduction conditions during firing are just right.

IT IS ALL MAGIC.

Naauao