Materials and making

Naturally occurring stoneware clay is not easy to find in the UK and so I use a manufactured body: Draycott White Stoneware, from Potclays in Stoke-on-Trent, which seems to suit what I want to do.

When it comes to earthenware things become more interesting as there are many natural clay deposits which will yield clays suitable for firing at earthenware temperatures. More work is involved in clay preparation and testing, but nothing brings a more intimate connection with your material than finding it, digging it from the ground and getting to know it’s characteristics as a making material.

I first tried working  with so called ‘wild clay’ at college when the foundation excavations for an extension to the buildings turned up a ready supply of clay to experiment with. However it was not until more recently, and particularly with the Lossenham Pottery Project, that I really started to work with wild clay more systematically. I sense it is the early stages in a long journey: learning to read the nature of different clays, and understand how to work with them, but I love the resonance there is in making things so directly connected to the specific places in the landscape.

My pots are largely wheel-made, although I also use hand building (coils, slabs) for some pieces. Having been taught on, and for many years used, an electric wheel I have more recently been working on a foot powered (treadle) wheel - similar to a Leach wheel - which I acquired many years ago and never had space to set up. It needed completely rebuilding but the medieval pottery project gave me both the excuse to do this and the space to use it. I am learning the adjustments of throwing technique required, and relishing the quietness and rhythm of the process.

When making on the wheel I like to get pots as close to the finished form as possible, and generally I prefer to do little, if any, turning (trimming the leather hard pot on the wheel).

With pottery what interests me most is form rather than decoration and so I tend to use glazes or slip decoration which respond to the form of the pot, rather than using the pot as a canvas for more designed decoration, whether figurative or abstract. In the medieval pottery (and the places where this influence finds its way into other pieces) I do like the use of applied, or incised, marks on the clay surface, though again most of these are about accentuating form.

For stoneware work I try to keep my glazes as simple and sustainable as possible, using basic ingredients such as feldspar, quartz, clay and wood ash, and sometime colouring from iron, and occasionally copper, oxides. With earthernware I use a simple transparent glaze (usually boron, rather than lead-based) over clay slip, in some cases with colour from red, yellow, or black iron oxide. These approaches provide a restricted palette, but encourage me to think about the decoration as an enhancement to the form of the pot rather than an end in itself.

One reason for keeping the glazing process simple is that the pots are being ‘raw-glazed’ - that is the glaze is being applied to the dried clay, rather than to clay which has been part-fired first (see ‘Firing’ below). This is not without its challenges: you can’t put watery glaze on a raw pot for too long before it turns back to mud!

All my pots are single-fired. The most widespread method of firing pots is to fire twice: first to around 900-1000°C (biscuit firing) before glazing and firing again (glaze firing). Single firing combines both these into one. The pottery is glazed while still ‘greenware’ (unfired dried clay) and then the glazed piece is fired in one go to its final maturing temperature.

Once, all pottery would have been single-fired but the two stage process of biscuit and glaze firing has some advantages. The main one is that the biscuit-fired ware is much more robust to handle, while still being porous enough to provide a good surface for glaze and other decoration. This became particularly important as pottery started to be produced in factories where it had to be moved around in large quantities and decoration became its own specialism within the factory process. It also has the advantage that catastrophic failure of a pot most often happens in the first firing when the ware is unglazed. In a single firing a glazed pot which breaks early in the firing (unless spotted and the firing abandoned) goes on to be fired until the glaze melts, potentially causing damage to both other pots and the kiln.

So, why single fire? One argument is the economic and environmental one: firing once uses less energy (and time) than doing one firing, then unpacking and repacking the kiln and firing again. It is not so simple as halving the energy consumption, but probably reduces it by about a third. Nonetheless, it does undoubtedly save energy. It also, of course, saves time.

Another reason is in the flow of the work. Making and finishing pots is a very direct, tactile, process and the feel of clay as it goes from wet and plastic to leather hard and then bone dry is part of that connection. I find that then to biscuit fire the pieces, and get back these strange, rather awkward, half-finished pots just to have to decorate them and fire them all over again, is an uncomfortable interruption. Finishing the making process and then just committing the pots to the kiln in one go - risks notwithstanding - feels a simpler and more natural process to me.

Most of my firing is done in an electric kiln, though for the Lossenham Project we have built a couple of wood-fired earth kilns, based on kiln designs of the medieval period. Learning the particular characteristics of these, and the technique of firing them, has been (and continues to be!) an interesting challenge.