A Potter's Guide to Clay Sources in the UK: Where to Find Local Clay and Suppliers

There is a stretch of riverbank, building site or back garden near you that would make pots. That isn't romance; it's geology. Britain is a clay country, from the blue-grey London Clay under the capital to the white kaolin of the Cornish moors, and potters have been digging locally for thousands of years. Buying a 12.5kg bag is convenient, and most of us do it most of the time. But digging your own, testing it properly and coaxing it into something that holds a rim is one of the most instructive things you can do with a bucket and a spade.

What follows is a practical route through the main British deposits, the permissions you need, how to test a sample without wasting a kiln firing, and where to buy clay and materials when digging isn't realistic.

Reading the Ground: Britain's Clay Regions

Clays come in two broad families. Primary clays stayed where the rock formed, which is why china clay and china stone are found in granite country: Cornwall, and the edges of Dartmoor in south Devon. They are coarse, lean and refractory, good for high temperatures but poor on their own for throwing. Secondary clays were washed away, sorted and re-deposited, picking up fine particles and plasticity along the way. Most of the workable pottery clay in Britain is secondary.

Use a geological map before you use a spade. The British Geological Survey publishes maps and a free online viewer, and your county's local geological society will happily tell you what you're standing on. Old place names are a shortcut too: Brick Kiln Lane, Claypit Lane, Pottery Row and Kiln Field nearly always mean what they say.

• Cornwall and south Devon: kaolin, china stone, and the micaceous red clays of the moors.
• The Bovey Basin and the Wareham area of Dorset: ball clays, highly plastic and strong, the backbone of British whiteware for centuries.
• London and the Home Counties: London Clay, Weald Clay, Reading Beds and brickearth. Variable, often iron-rich, frequently good for earthenware and raku bodies.
• The Midlands: Oxford Clay and the Etruria marl that built the Staffordshire Potteries.
• Yorkshire, Derbyshire, Scotland and South Wales: coal measures fireclays and shales, often decent stoneware material.
• Almost everywhere: glacial till or boulder clay. Unpredictable, full of stones, but frequently workable after sieving.

Permission Comes Before Digging

Ask the landowner, every time, even for a small sample. A farmer, a golf club or a housing developer will often say yes to a bucket or two if you explain what you're doing and fill the hole back in. Never dig in a Site of Special Scientific Interest, a scheduled monument, a nature reserve or on National Trust land. Avoid canal and river banks, where disturbance can cause real damage, and don't take clay from beaches or cliffs with protected status.

Good places to ask about are your own garden, an allotment, a field margin, a pond dredging, or the spoil heap of a building site. Get the site manager's permission and keep clear of machinery. If you're unsure whether a site is protected, or what the rules are for removing material, take proper advice before you dig rather than after.

From Bucket to Test Tile

Raw clay straight from the ground is usually too wet, too stony or too short to use. Work through these steps and label everything, because you will not remember which bucket came from where.

1. Slake it. Break the clay into lumps and cover with water in a lidded bucket. Leave it for days, or over winter outdoors. Frost and time break down the structure far better than any tool.
2. Sieve it. Push the slurry through an 80 to 120 mesh sieve to remove grit, roots and stones. Pour the result onto a plaster bat or a cloth-lined tray to stiffen.
3. Test the plastic state. Wedge it and roll a coil as thin as you can. A long, flexible coil suggests good plasticity; one that snaps at 10cm needs help.
4. Make test tiles. Press out flat tiles roughly 10cm square and about a centimetre thick. Scratch a 10cm line across each one and label the clay and the intended firing temperature.
5. Measure shrinkage. Measure the line once bone dry and again after firing. A drop from 10cm to 9cm is 10 per cent shrinkage; anything over about 12 per cent total is asking for cracks.
6. Check absorption. Weigh a fired tile dry, boil it in water for an hour, leave it to soak overnight, then weigh it wet. A big gain means a porous earthenware; almost none means a vitrified body.
7. Fire a range. Fire identical tiles to several temperatures, for example around 1000°C, 1100°C and 1200°C. Watch for bloating, warping and colour change.

Test three tiles before you commit a kiln load. A clay that throws beautifully at 1100°C can blister into a grey sponge at 1250°C.

Adjusting a Difficult Clay

Most local clays need a nudge. Add 10 to 20 per cent fine sand or grog to open up a sticky, over-plastic body and reduce shrinkage. Add a little ball clay, or a very small percentage of bentonite, to short clays that refuse to hold a shape. Feldspar or nepheline syenite will help a clay mature at a higher temperature, while blending two local clays is often the simplest fix of all. Keep additions by weight, record them, and retest rather than guessing.

Silica dust is the real hazard here. Sieve and mix wet, wear a properly fitted respirator when handling dry powder, and never dry-sweep a workshop.

UK Suppliers Worth Knowing

When time or consistency matters more than the romance of digging, these are the names most British potters rely on. Many stock small test bags as well as full boxes, which is the sensible way to try a new body.

• Valentine Clays and Potterycrafts, both in Stoke-on-Trent, for a wide range of prepared bodies.
• Scarva Pottery Supplies in Northern Ireland, a strong choice for clay, glazes and kiln equipment.
• Bath Potters' Supplies, CTM Potters Supplies in Dorset and Clayman Supplies in Kent for southern potters.
• Hot Clay for the Midlands and north, and Cromartie for kilns and ceramic materials.
• Sibelco for industrial kaolin and ball clay, though they supply at trade scale rather than to hobbyists.

Start Small, Keep Notes

Dig two buckets from one spot, process them properly, make a dozen tiles and fire them alongside a clay you already know. Note the location, the depth, the date and every addition you make. Local clay rarely behaves like a commercial body, and that's the point: it carries the colour, grit and character of a particular place. Some samples will end up in the garden. One or two will become pots you keep.

Photo: Beeki / Pixabay