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 to 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 body; ogranic matters burn out.

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

(all moisture left from the ware around 200C, door and peep hole 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 siica inversion goes too fast.

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

caution: pin holes, glaze surface insufficient might appear if soak at the end does not done 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 relaese.)

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.