Clay For Pit Firing

[Darcy Kane]

I have a friend who is obsessed with doing pit fires but using raku clay has turned out less than desirable results.  Does anyone have a clay body they have liked for pit fires?

[Evelyne Schoenmann]

I can't see in your profile where you are living, Dharsi. I usually take a clay that's made here in Switzerland for a company that produces chimneys. It has 60% grog in it ( 0-1,5 mm). It never, ever cracked in the fire.

Could you maybe tell us where you live, so maybe people who knows what kind of clay there is in your country can help you with clay names. Thank you.

If you live in the States, Marcia will be the perfect person to help you.

 

Evelyne

[Marcia Selsor]

I use locally dug clay and , if necessary, some fine grog.A red earthenware with an aggregate will work. If you are burnishing, use a very fine aggregate. Some people use pumice fir that purpose.

 

Marcia

[Frederik-W]

I am not sure what you mean with "less than desirable results".

Does your stuff crack or explode due to thermal shock?

Or don't you like the colour or some other effect of the fire on the clay?

 

I use a very course raku clay (has course grog) and it is very resistant to thermal shock.

I do not bisque my pots beforehand, I fire them green.

Of course you need a gradual temperature rise, not direct, immediate or uneven heat or it will crack & explode.

If you cover your work in e.g. sawdust or mulch and make the fire on top, the sawdust acts as a protective thermal blanket from the immediate heat of the fire above. By the time the fire burns down to your pot it has gradually warmed.

 

The same gradual heating applies to open fire. I put the pot in the middle, make fire around it and then gradually bring the fire in closer to give it time to adjust to the temperature.