Digitalfire Ceramic Glossary

Logged in as Level 2 access: Logout


You should always be testing. But it is wasted without an audit trail. Document your lifetime of recipes, firing schedules, test results, pictures and much more in a private account at insight-live.com. It is the future, the next step after desktop Digitalfire Insight.

Watch the video, learn more or sign-up at http://insight-live.com.

Celadon Glaze


A green or blue-green reduction fired glaze that has been stained using iron oxide. Celadons were first developed by the ancient Chinese. The celadons that potters are accustomed to firing today are glossy transparent whereas the ancient versions were more waxy and opaque. Thus there is dispute among practitioners and purists about what exactly a celadon really should be or what glaze can truly be labelled 'Celadons'. There are many books and webpages on the subject.

Typically celadon glazes are employed on porcelain but can also be used effectively on stonewares. Modern Celadons usually possess their high gloss because of high amounts of sodium and potassium, these oxides also cause the crazing often seen. However this problem can be solved by substituting some of the Na2O with lower expansion MgO or CaO and increasing the SiO2 (using ceramic chemistry calculations of course). Celadons have traditionally been fired at cone 10 but lower temperatures are possible with the addition of more flux (e.g. Gerstley Borate).

Blue celadons typically have high sodium/potassium, high silica, not too much iron, and low titanium (Grolleg kaolin is a good option to minimize the TiO2). Some claim that a little tin oxide and/or barium carbonate will help with the blue color. Some people are investigating creating celadons for cone 6 oxidation using stains to impart the color.


By Tony Hansen

Out Bound Links

  • (URLs) Celadon on Wikipedia
    http://en.wikipedia.org/wiki/Celadon
  • (Glossary) Crazing

    Small hairline cracks in glazed surfaces that usua...

In Bound Links


Pictures
Celadon cone 10R glaze (about 3.5% iron oxide) on a buff firing reduction stoneware with G1947U transparent liner glaze

Click for 565% larger

Crazing in cone 10 reduction celadon glazes, especially on porcelain, is common because they are high in K2O/Na2O. However this problem can be solved by increasing the SiO2 and substituting some of the KNaO for lower expansion fluxes like CaO.

Click for 488% larger

Close-up of cone 10R celadon bubbles suspended in the glass. This is happening because this glaze lacks flux. In the upper half they are more evident (double thickness).

Click for 563% larger

GR10-E Ravenscrag:Alberta Slip (50:50) celadon with 10% added calcium carbonate produces an overly melted glaze.

Click for 510% larger

Ravenscrag GR10-E celadon glaze (50:50 Ravenscrag Slip:Alberta Slip) at cone 10R on porcelain (right) and stoneware (left).

Click for 677% larger

GR10-E (50:50 Alberta Slip:Ravenscrag Slip) celadon at cone 10R on a white stoneware and a porcelain.

Click for 710% larger

50:50 Alberta Slip:Ravenscrag Slip cone 10R celadon on iron stoneware, buff stone and porcelain.

Click for 534% larger




Feedback, Suggestions

Your email address

Subject

Your Name

Message


Copyright 2003, 2008 http://digitalfire.com, All Rights Reserved
Get a free INSIGHT software trial

INSIGHT is ceramic chemistry
calculation software that runs on
Windows, Mac and Linux and talks
to this web site. ()