Celadon
Celadon glazes have been made in Asia for centuries. The light green colour is produced by a very small quantity of iron in the glaze and clay when the kiln is fired with a reducing atmosphere. This reduction occurs when smoke present when the glaze is melting between 1100 and the top temperature1300 degrees centigrade).
My Celadon is a simple one typical of those made in China and Southeast Asia. This family of Celadons can vary between the green shown in the picture, grey, tan, and grey/blue, depending on the particular combination of clay and glaze materials as well as the firing pattern.
Chun
Chun is a similar glaze to Celadon except that it tends towards a pale blue rather than green.
White
The whiteness of this glaze varies with temperature and the atmosphere and sometimes has a faint blue or yellow cast.
Eggshell
Eggshell is very responsive to variations of kiln atmosphere and thickness in application.
The colour and matt surface comes from Dolomite and Talc.
Black and Blue
‘Black and Blue’ is made with two glazes. The pot is first dipped in a thin concentrated of oxides which give a matt black outside.
The inside is then glazed with white which is stained a variable blue by the oxides underneath it.
Black
Black comes from combining iron, copper, manganese and cobalt in a lower-melting glaze.
As with Black and Blue, the pot is glazed again on the inside with white. This becomes a broken cloudy colour and often shows pink tones because of the presence of the copper.
Raw Blue
These pots show a lot of unglazed clay. I tend to glaze this series only where it really matters on the working surfaces.
It is interesting to note the difference between this series and the wood fired pots. Raw Blue is fired in the gas kiln and is not glazed by any wood ash blowing through the kiln.
Tenmoku
Another traditional Chinese/Japanese glaze, the red colour of Tenmoku comes from the surface oxidation of the iron in the glaze as the kiln cools down.
Traditionally the red is called Kaki and the name Tenmoku is reserved for the glaze when it is black. In New Zealand, the whole family of iron rich glazes are called Tenmoku.
Shino
Shino is another traditional Japanese glaze. Its main ingredient is a type of feldspar.
Its colour, like many stoneware glazes, varies according to the atmosphere in the firing. More free carbon (smoke) and a higher temperature produces a bright orange. Oxidation can make the glaze more pale or white. Often a pot will show a wide variation in this colour range.
Wood Firing
Firing with wood as fuel has the interesting effect of partially glazing the clay that is exposed to the flames and wood ash. This can be seen here in the burnished surface on some parts of the pot’s surface.
Where this burnish is thickest more wood ash has combined with the silica in the clay to make a brown glaze. The lighter areas have less wood ash.
These patterns occur because the pots are more or less shaded by other pots next to them in the firing. These patterns are a natural result of the flame pattern and become a record of the process of firing.
The pots are knowingly incorporating an ‘unintentional’ decorative element. My preference is for these traces of the firing to be reasonably subtle.
By contrast, a very old (5th Century) wood-firing system – Anagama – takes up to 10 days to achieve temperature but in the process produces spectacular glaze effects because of the prolonged exposure to the wood ash at very high temperatures. My firings take only 15 – 18 hours and have a less dramatic effect on the clay.
