4.3 Firing Clay

Firing Ceramics

Key Chemical Changes in the Firing

0-100C: moisture escape

caution: ware easy to explode if moisture traps inside the pots.

(door ajar, peephole open, pre-soak regarding the thickness of works. I tried cone 6 red clay with fine grog,  artworks thickness between 1- 3cmm, pre-soak takes 4 hours.)

100-300C: chemical water and gases start to leave the body; organic matters burn out.

caution: ware easy to explode if moisture traps inside the pots.

(all moisture left from the ware around 200C, door, and peephole is closed).

500-600C: silica inversion, crystals from clay to ceramics, shrinkage/expansion 3% begin at 575c (should be fired slowly or soaked for 1/2 hours)

caution: ware easy to crack if silica inversion goes too fast.

1100-1650C: needlelike glass formation depends on the clay types, go slowly, longer soaking might need for some special glaze.

caution: pinholes, glaze surface insufficient might appear if soak at the end does not do correctly.

In general, 

Normal Bisque Firing for thin or slip casting works can go up to 100C per hour until 600C, after that put on full power 150C/h.

Bisque Firing for thick or sculpture works should not go more than 50C per hour until 600C, after that put on full power 150C/h (mush sure soak around 90C to allow moisture release.)

Glaze Firing if work already bisque, can go up to 125C until 600, after that put on full power. Unless special glaze effect might need a hold in higher temperature.

Claynotes Index: