kiln disasters

[roslyn89]

Hi, Im a newbie to this forum and also to ceramics. here's my problem.
Im having lots of explosions/ shattering and simply chunks of clay flaking off while firing.
Its an earthenware clay fired to 1260, I dont know if its just not dried out pretty sure theres no air bubbles there is however a broken brick in top of kiln which is slowly crumbling away. any help is appreciated. thanks.
Ill introduce myself later, right now I have a kiln to clean up!

[Andy Clift]

The ware needs to be completely dry before you fire it. It should not be cool to touch, that would signify moisture still in the piece. Also you need to preheat the kiln and fire slow at the beginning of the firing. See this link for detailed tips.
Firing Electric Kiln - kiln sitter or electronic control, instructions, tips and issues

[roslyn89]

Thanks Andy, I thought that moisture could be the problem even when it seems completely dry, the trouble is my workshop has no heating so it takes so long to dry anything.

[eli griggs]

You might consider building a cabinet, with a low wattage bulb, for a heat source, that you can move pieces into, after several days of air drying.

[jbittkau]

Hi Roslyn - two things come to mind which can cause explosions and that is moisture as well as contamination of the clay with plaster of paris. The temperature 1260 - is that Fahrenheit or Celsius. It seems too low for Fahrenheit and too high for Celsius if you are using earthenware clay. What temp did your supplier recommend? The drying cabinet sounds like a good idea - otherwise you have to have cultivate that most necessary virtue for good pottery - patience - and allow a much longer drying period. Are your pieces of uneven thickness? I do find if my beginner students have pots with very thick bottoms and thin walls, we risk cracks but moisture is usually the cause for explosions. I fire my earthenware to 1000deg C and glaze at 1100deg C and get consistently good results.