Smoke Fired Pottery

Smoke-fired pottery, sometimes called pit-fired pottery, is the oldest pottery known to man.  Any pot fired in a pit, as were the most ancient of pots, will have flashes of dark smoked areas where the smoke has been absorbed into the pottery from the firing.

This random pattern can be seen on many ancient pots and on pots fired nowadays in many communities where pits (open firing) are still used to fire the work.  In today’s smoking tradition the aim is to harness smoke, only allowing it to flow where it is desired.  Some potters achieve this most eloquently whilst I only manage to partially harness the smoke, but I am equally enthused where part of the pot has been unrepentantly claimed by the smoke creating a different result every time.

Making the Pot

I would like to say that I throw each pot individually, but in fact the narrow base makes it difficult to throw.  The 'master' pot that I made I threw upside down and collared the clay in as it grew.  I had to hand-coil on top of the collared clay and drag the clay up collaring in again and again until it was sufficiently large.  I waited for the pot to dry somewhat before adding a base (to the top) which I had rolled out.  I only hoped I had not made the base too narrow and that the pot would stand up once turned over.

Before I had a chance to test this I decided to make a mould from the pot as the throwing process had been so time consuming.  I placed a cottle around the pot and poured plaster into the volume having secured gaps with soft clay.  It is always good to ensure your plaster has not gone off when you go to this trouble as plaster which has been lying around in the workshop for over a year undoubtedly will have.  The drawback with old plaster is that it never really sets and if it does is powdery and crumbles.

Creating the Mould

Having removed the cottle I was pleased with the mould which I cleaned up thoroughly, removing the thrown pot and discarding it.

Now I can use the mould to create hundreds of pots all the same.  It is the smoking which makes each one different, and the type of smoking I decide to use which will determine the end result.

Once the mould had dried, which took a couple of weeks in a dry warm atmosphere, I work into the mould with Earthstone clay.  This clay has a wonderful white appearance but is heavily grogged which means the clay will absorb shock more easily and is likely to withstand the smoke firing process without cracking.  I either coil into the mould or place sheets of clay inside dragging them together with a kidney.  I try to ensure the base is thicker but if it is too different from the body it will create stress in the pot and this will cause it to shatter in the electric bisque firing.

Burnishing

It is all about balance, too much or too little all along the way can be disastrous!  When the pot has dried sufficiently to be removed from the mould I place it upside down on a banding wheel and tidy it up using a kidney to drag clay over the surface until it is flat. The stony clay makes a coarse scraping sound which is very satisfying!  While the Earthstone clay is perfect for helping to prevent cracking during firing, it is not a desirable surface to smoke onto.  A really smooth surface which will absorb the smoke and shine when waxed is required.  To achieve this I make a slip from Earthstone by sieving out the grog and applying it to the pot in creamy liquid form.

Two or three layers on the surface are applied by banding onto the pot, leaving each layer to dry a little before applying the next.  When the slipped surface is leather hard I burnish it to create a smooth surface.  This will enhance the smoked pattern after polishing with beeswax.  Burnishing is achieved using the back of a metal spoon, rubbing it relentlessly over the surface of the clay until it is smooth to the touch.

Firing

The work is bisque fired in an electric kiln between 950 and 1000ºC.  The higher the temperature of bisque firing, the less porous to smoke the work will be.  After the electric firing, the smoke firing is carried out in a steel dustbin of the type used for burning garden rubbish.  I do the firing or the smoking as I prefer to call it at the bottom of the garden.  As my desire is to create smoke rather than fire I try to get as far away from the house and neighbours as possible!  Pots are fired singly so that, to some degree, I can control what is happening and do not threaten one pot with another that may crack during the process.  Before this takes place I liberally cover the pot in slurry.  The slurry I choose to use will be heavily grogged and anything in the workshop with grog in it will do.

Before the grogged clay fully dries I scrape lines through the slurry onto the pot with a wooden skewer, being careful not to scratch the pot.  Where the slurry has dried quickly the lines may be disturbed as chunks of slurry fall off.  Sometimes I recover these areas by smearing more slurry on top and dragging fresh lines through, and other times I decide to leave them to the smoking process for pattern.  It is important for the pot to dry thoroughly before smoking since a wet pot is more likely to crack.  However, I usually place the pot in position while it is still damp as moving it when it is dry often causes the slurry to drop off in chunks.

Smoking

Into the bottom of the bin I place bricks to stand the pot onto, raising it above the base of the bin so that air circulates and keeps the smoking going for as long as possible.  I fill the base of the bin with paper and sawdust soaked in white spirit to help it set alight. The choice of smoking material will affect the end result.  I used to use paper and the different types of print on magazines will often give interesting results as the smoke sinks into the wall of the pot.  Heavily printed magazines may result in copper deposits in the smoke etching the pot surface.  You can add to this by wrapping copper oxide in paper and letting the paper burn away, burning the oxide into the pot.  Burning sawdust will give varied results depending on the nature of the wood used.  Ensure you are not burning MDF, though!  I have found the most stunning results come from burning garden leaves and dried garden cuttings.  The smoke they give off is tremendous and often means the pot will only require one smoking.

After placing as much material as possible around the pot I light from the bottom at equal places around it.  This is made easy by using a garden incinerator as there are holes around the base where you can light the fire.  The holes act to circulate some air into the bin keeping the contents burning.  Smoking is desired rather than burning.  A fast light up resulting in leaping flames needs to be calmed immediately as sudden uneven heat will cause the pot to crack.  Once alight, I control the flames by placing the lid onto the bin if they become too fierce.  However, I have found that by burning garden debris the desired smoking is quickly achieved.  Once the pot is simmering away I leave it and only go back to top up with cuttings.

Naturally with this type of firing there is an element of chance involved, depending on the weather.  The outcome of a good firing however, is a range of light and dark areas, some deeply blackened contrasting with almost white areas where the clay has been covered in slurry and the smoke has not penetrated.  I never take the pot out until the following day as by leaving it in the bin with the lid on overnight the smoke is allowed to permeate the clay surface and blacken it more and more in the areas not covered in slurry (the scratched patterns and lines).  The smoke firing usually takes 2 to 3 days to complete; the work is assessed each morning and maybe re-fired several times until judged ready.

Cleaning

Once I have assessed the work and decided whether the process is complete, I can remove the slurry which remains on the pot surface.  This is done initially by chipping it off.  It will have dried onto the pot like dried mud and should come off in pieces. However, stubborn pieces will have to be soaked and scrubbed off in the garden.  I use a baby bath, place the pot in it and shower it down with a garden hose.  It will then need to dry for a couple of days somewhere warm, such as an airing cupboard.

Polishing

The final process is a satisfying polish with natural beeswax.  Up to three layers applied and then polished on top of each other will give the burnished pot a wonderful shine.  The smell of the pot will be a give-away for a long time, but I love that burnt smell mingled with beeswax which makes it so authentic.