I decided to try build a home-made pottery kiln in my backyard. Keep in mind that the method outlined below is not a suitable substitute for an electric kiln, since you will never reach the high temperatures required for a proper firing. Any pottery you make with this method will still be fragile and susceptible to moisture, so keep any finished pieces indoors, or get them fired properly.
Be sure to check out this video by Simon Winder, which contains lots of useful information.
- Clay bricks: any old bricks will do, but clay bricks would be ideal as they provide better insulation.
- Pick and shovel: for digging a deep hole. Enlist the help of a spouse / SO as necessary.
- A large flagstone or roof tiles, for covering up the kiln once it starts burning.
- Lots of sawdust. Wood chips and small kindling will come in handy too.
Note: I recommend avoiding pine sawdust, which leaves behind a residue.
For starters, I created a few simple test pieces. If anything were to go wrong, I wouldn’t be devastated by the loss:
A simple mask made with paper clay. Height: 30cm. No under glaze. This piece was left to dry for around 24 hours prior to firing.
More test pieces: Two small, thin ‘shards’ of paper clay with a blue underglaze, decorated with petroglyphs. The rectangular piece on the right is made of ordinary clay with the same blue under glaze, depicting a hoplite. All these pieces have dried out over a period of several weeks.
A tablet made of paper clay, around 25cm in height and less than 1cm in thickness. Blue under glaze, decorated with scratched out petroglyphs.
Once the hole was ready I lined the sides with bricks. The kiln should be large enough for one or two pieces per layer, up to three or four layers deep. The cat is there for scale and decoration, and should not be left inside the kiln upon commencing with the firing process.
Piling on the bricks, while making sure the structure is stable.
The kiln is more or less ready. I placed a few bricks at the bottom for better heat insulation before filling any remaining gaps with soil as best I could. The flagstone on the right serves as the cover.
I then started filling the kiln with sawdust — and lots of it! You can also use wood chips or kindling. Upon creating a base base layer of sawdust, I began placing my pottery pieces inside, leaving a large space around my pieces, so that they are properly fired from all sides. Each piece was cover with more sawdust before adding more pottery pieces. Keep in mind that that whole structure will collapse as the sawdust burns up.
Just about done. I used nearly a whole refuse bag of sawdust to fill the kiln.
Next I built a small fire. Use kindling if you have it, though firelighters and charcoal seemed to work just fine.
Once the fire and sawdust were ignited, I covered the kiln, leaving just a few small gaps. Whoops — waaaaay too much smoke!
Lining the sides with more bricks helped reduce smoke output. I may be wrong, but lowering oxygen intake may also help achieve a slower burn, which is what we want. Ideally, only a little smoke should come out of the kiln.
Amazingly, the kiln ended up burning for over 24 hours! When I finally opened it up I was pleased to find that most of the sawdust had burned up, leaving behind ashes and my pottery pieces. The pine sawdust had left behind lots of resin on the bricks and flagstone, so I recommend a different type of wood if possible.
Pottery test pieces, shortly after being removed from the kiln. The thin paper clay mask had a developed a crack, but the other pieces showed no structural damage. The large tablet (left) shows some discolouration, which I think was caused by pine resin. All pieces were still very hot to the touch, so use a dishcloth or gloves when removing them. While certainly drier and harder, the pieces are still brittle. Keep them indoors and out of harm’s way. Better still — have them fired properly in an electric kiln.
Two more pieces I made shortly afterwards. Note the weird discolouration caused by the resin which — in this case at least — created a pleasing effect.