Dig, make, fire

This week I finally lit a fire I had been planning for many moons. My collection of unfired pots, made from foraged clay, has finally been fired! To go from digging clay to producing useful and maybe even beautiful items is extremely satisfying and something I’d love to inspire you to try out. This is an activity which connects us to our landscape and our ancestors-people have been digging wild clay and making pots in the UK for at least 6000 years. Collecting and working with clay is also a great activity to do with children.

Please note that this is a journey of discovery I am sharing- I do not claim expertise!

FINDING CLAY

Around Bristol, we are blessed with oodles of clay (which doesn’t feel like such a gift when gardening). Dig just about anywhere and you’ll soon hit clay. In other parts of the country, you might need to try next to rivers or streams, or ask local geologists for advice. If you’re not sure if you have clay, play with a small bit and see if you can manipulate it into simple shapes. You want to be able to wrap a pencil thickness sausage of it around your finger, without it falling apart.

PREPARING THE CLAY

Once you have found your clay, you need to work through it, pulling out impurities such as roots or stones. The clay I dig has always been damp (this is the UK after all) and so I have used the following process to prepare it. Firstly, you will then need to begin to homogenise (make it all the same!) by kneading until the clay is of even consistency. If your clay cracks easily while you knead, it may need a little water adding. Conversely, if it is very sticky or even gloopy, you’ll need to let it dry out somewhat.

At this point you need to think about temper… this is not an anger management issue but the addition of non-plastic materials, such as sand, to the clay. This helps prevent the clay cracking as it dries or during firing. The amount of temper needed varies with each clay, as some clays have tempering materials in them naturally. Experimentation is needed to work out the best amount of temper to add, but a starting point is 1 part temper to 4 parts clay. If your clay still cracks, add more temper, but don’t go more than 30% temper or your clay may lose too much plasticity.

Before you make anything from your clay, give it a final knead with the aim of removing any air pockets, as these can lead to explosions when firing

MAKING THE POTS

I’d recommend starting out with simple pinch pots. Just take a small ball of clay and shape it into a pot shape with your fingers. Aim to get consistent thicknesses to your pot’s walls and base. For cup-sized items, I try to limit the clay thickness to 1cm. Thicker pottery needs much longer to dry and fire. If you or the kids are making small sculptural items, hollow out any thicker sections. As you progress, it’ll be worth looking up techniques for larger pots, such as coiling or slab building.

Your items need to be thoroughly dried before firing. It is best to do this slowly in a cool, shady place, to avoid cracking. A couple of days before firing, I leave my dried-out pots on our radiators or on a sunny windowsill, to try and drive out any remaining moisture.

FIRING

There seem to be as many ways to fire a pot as there are pot styles. Although I have had good success with open fires, I favour having the fire in a pit as higher temperatures can be obtained with less wood. Even so, make sure you have plenty of firewood prepared!

Choose a day with no wind or a gentle breeze. Strong winds will make the fire harder to control. My pit is 2 feet in diameter and about a foot deep, which enables oxygen to get into the fire.

Begin the firing with a slow and gentle preheat, gently warming and rotating the pots around a small fire for at least an hour. This aims to push any last bits of moisture out of the clay- moisture is the main reason pots crack when fired. After preheating, build up the fire by gently adding firewood, until the pots are fully covered by the fire. Once the pots begin to be hot, do not attempt to move them as they are extremely fragile at this stage.

The fire needs to be glowing red hot, which is around 540°C, at which point the clay begins to irreversibly change at a molecular level into stone-like pottery. There are many different lengths of time advised for the actual firing, from 20 minutes within a ‘white hot’ fire to several days. My pots turn out well after around two hours within a red to white hot fire. You may need to add more wood to get the heat and time required. I let the pots cool down within the embers, sometimes gently lifting them to the surface as they cool, if I’m in a hurry.

THE RESULTS

The resulting pottery is a delight to handle the first time, as you see how each piece has fared. I have been lucky so far to have few breakages, perhaps as I am careful with preheating.

Pottery made in this way is termed earthenware. As it is not glazed, it is porous. This can be useful for low tech refrigeration and as part of a water filtration system.

The blackened areas are where less oxygen reached the pots. Controlling the oxygen levels is used by experienced potters to vary the finish of their pots. This is one of many variables I hope to experiment with in future firings. There are also many other aspects to the clay preparation and firing which can be explored, from firing times and temperatures, to using different tempers and natural colourants.

I hope this has given you some inspiration to get digging, making and firing!

Bibliography and further information

Blankenship B and Blankenship R. 1996 Earth Knack Stone Age Skills for the 21st Century

https://www.youtube.com/c/AncientPottery/playlists