search  current discussion  categories  kilns & firing - pit firing 

pitfire! how we did it.

updated thu 14 may 98


Justin M. Smtih on wed 13 may 98

Hello to all you Clayarters,
Here is how we did the pit fire at Genesis Clay Works, O'Neals, CA, on May 2 &3,
1998. This is the posting I promised Sunday but was unable to send. Sorry to all
how was looking for it.

This year's pit fire was the third annual pit firing hosted at Genesis Clay
Works. The first year we had no idea what we were doing and didn't do to bad wit
only 13 broken pieces out of some 175. Last year we only had 4 broken pieces an
this year NONE! And this year we got the best color I've ever seen. The followin
tells about the process of the pit firing at the studio.

The Pit:
The pit is self is 4 feet high, 4 feet wide, and 16 feet long. 2 feet of the pi
is below ground level and 2 feet are above ground level with gradual sloped
ends. We found that this allowed better air flow and also the banks made it eas
for loading and unloading of the pit. The pit is dug in the same direction as
the prevailing wind to again for better air flow. The the same pit is used ever
year, we don't re-dig it. This last year we lined the pit with corrugated steel
sheeting held in place with steel fencing posts to prevent the side from
collapsing during firing.

Preliminary Loading:
The first year everyone brought wood and we also have some heavy oak on the
property. In loading the heavy wood got thrown in the bottom at random. We
found that this slowed down the firing and prevented good flow through the pit.
the last two years my father and I have per loaded the bottom layer of wood.
First we lay down old shipping pallets and stuff them with newspaper. This
provides an air space for the fire to travel through the bottom of the pit. The
a layer of light brush is placed on to of the pallets. The heavy wood, 3 to 8"
round oak, cedar, old fence posts, what ever available is the laid long ways the
length of the pit. In loading the bottom layers of wood this way the fire flows
through the pit much faster, and allow a mush more even firing. The first year
the pit fired from one end and burned slowly to the other. Now the whole thing
burns through within the first half hour that then the whole pit burns down
evenly. This we found to be every important!

Preparation of the Pots:
We have about 30 - 40 people attend every year, some student, some professional,
and many in between so we get all kinds of pots to fire. Many of the pots are
stoneware that has been bisque fired. (Caution: avoid B-mix and other fine bodie
clays) Stoneware with sand or grog works best. We have a salt and copper wash
that some people pure over the bisque ware. It is rock salt and copper carb.
mixed in water but don't soak the ware with water, it will blow in the firing.
Some pots have Terra Sig on them, white takes the best color if you want the red
and oranges from the firing, but red and orange Terra Sig work fine also. At
Fresno City College where I attend school and many of the students attend the
firing we have a Sagger Slip we spray on green ware and then bisque fired. This
gives beautiful color but leaves a rough surface on the pot. Some people have
used red earthen ware that they burnished and it took the color and smoke well
and gave interesting affects.
Some people choose to bring their pots pre wraped in grocery bags with cow dun o
other combustibles rapped around the pot. Don't forget about using dry seaweed,
banana peels, and copper wire to wrap around pots, they al give interesting
Sagger Fire Base Slip:
Gerstley Borate----------25.
Copper Carb.-------------5.

All the pots are set on one bank of the pit and all the wood is piled on the
other bank. A bed of straw is laid down. Then with two people loading the pots
are loaded, staring at on end working their way back to the other end. One perso
loads the pots in a signal layer as close together as possible while the second
person works small pieces of wood in and around the pots. All the pots are then
covered with three large bags of vermiculite. Then course sawdust mixed with
copper carb. is layered over the pit. We use about 5 lbs of copper carb. with
the size of our pit. The pit is then filled to the top with small to medium siz

The pit is covered with corrugated steel sheeting supported buy 3" steel pipe.
The edges along the bank are covered with dirt to seal of the pit. Ends are lef
open first. The pit is lit at on end, the end the wind is coming from if there
is any. And way she goes. After the pit is burning well sheets of corrugated
steel are placed at the end if there is a lot of wind but be careful not to
damper the fire to much.
The pit is loaded around 11:00 and burns all night. The second day the pit is
unloaded late that afternoon. If you have and question or would like to be adde
to the mailing list for next years pit fire feel free to email me Subject line: Pitfire

Justin M. Smith, Genesis Clay Works