Pottery: a guide to sawdust firing

Sawdust firing gives pots a rich, black surface without the use of glaze. These tips will help you achieve this desired effect properly.

Because the kiln reaches a relatively low temperature, pieces fired by this method are not suitable for holding liquid or food. The clay must be completely dry and not too thickly crafted, otherwise cracking will occur.

Burnishing before sawdust firing gives an attractive, polished finish. This is done while the pots are still a little moist so that the burnishing tool slips over the surface freely.

• You will know that the surface is at the right stage if the clay gives slightly under the pressure of the tool without distorting the pot's shape.
• Burnishing can be done with a teaspoon, a lapidary stone, a small light bulb (large ones are too fragile), a piece of glass or a flexible piece of hard plastic.
• As you continue to burnish a surface, it will become shiny and smooth like polished marble.
• It is necessary to repeat this process a couple of times over the drying period to maintain the shine.
• You may choose to polish part of the surface and leave other areas unburnished as a contrast.

1. Put a thick layer of sawdust over the floor of the kiln.
2. Aim for seven to 10 centimetres (three to four inches) deep, then place the pots inside, leaving a few centimetres of space between them so that you can pack sawdust around and inside every pot.
3. If you have a number of pots to fire, stack them in layers on chickenwire supported between the bricks.
4. Add sawdust as for the first layer. It is best to use sawdust from softwood trees because hardwood sawdust smells strongly when it burns. The best approach is to experiment and note the effects you can achieve with sawdusts from different trees and of different particle sizes (from wood shavings to fine dust).
5. It is advisable to wear a dust mask while packing the kiln.
6. When all the pots are in the kiln, finish with about ten centi­metres (four inches) of sawdust on top of them.

1. Add a layer of crumpled newspaper and some small twigs on top of the sawdust to start a fire.
2. Once the fire is going well and the sawdust is alight, put the lid on, leaving a small air gap until the sawdust has burned down a little.
3. The lid can then go directly onto the top layer of bricks.
4. If the fire is burning too quickly, fill up holes between the bricks with a mortar made of soil or sand and water. The kiln should burn very slowly and with very little smoke after the initial fire has diminished. It may take up to 36 hours for the sawdust to burn away.
5. To check that firing is complete, remove the lid to see whether all the sawdust has burned or test the heat level from outside the kiln (as the sawdust burns down, the upper part of the kiln cools). The slower the kiln burns, the blacker the ware will be.
6. If you want to vary the colours of your pot, try bundling up small handfuls of sawdust in newspaper, or mix shavings and sawdust.
7. Once the pots have cooled completely, clean the surfaces with a soft cloth. Resin from the sawdust can leave attractive, iridescent markings on the pieces.
8. If too much resin builds up, gently remove it with a kitchen scourer. When removed from the kiln and cooled, burnished surfaces can be finished with a layer of wax — natural or silicone floor wax — which buffs to a deep shine.