Walk into any pottery supply shop and you will find shelves of clay bags in reassuringly earthy colours, each with a code and a firing range printed on the side. Choosing between them can feel like a quiz you did not revise for. For hand builders the choice matters more than for throwers, because your fingers, not a spinning wheel, are doing all the work. The right clay body will bend, hold and dry in ways your project needs. The wrong one will crack on the join, slump on the shelf, or refuse to take a glaze nicely. Here is a practical look at the three families you will meet most often in the UK, and how to match them to pinch pots, coils and slabs.

Earthenware: The Forgiving Starting Point

Earthenware fires low, usually somewhere between 1000°C and 1150°C, which means it stays porous and relatively soft. It is the clay most people meet first, and with good reason. It is plastic, it takes shape quickly, and it tolerates a certain amount of enthusiastic handling. Red and buff earthenware are widely available and inexpensive, and many community studios fire it because it is gentle on the kiln and quick to reach temperature.

Its weaknesses are worth knowing before you commit. Unglazed earthenware absorbs water, so a bowl left to soak will eventually seep. It chips more readily than higher-fired clays, and it is not frost-proof, so garden pieces need care. For decorative work, pinch pots, tiles and low-fire glazing experiments, it is hard to beat. For a mug you intend to use daily, it works only if the glaze is sound and the piece is fired properly.

Stoneware: The Reliable All-Rounder

Stoneware is the workhorse of hand building. Fired between roughly 1200°C and 1300°C, it vitrifies — the particles fuse enough that the body becomes dense and strong. That makes it suitable for tableware, ovenware, planters and anything likely to be knocked about. It comes in buff, grey, brown and near-black, and in smooth or grogged versions.

For hand builders, the appeal is its balance. A good mid-fire stoneware is plastic enough to coil without fighting you, firm enough that a slab holds its shape, and tough enough that a slightly uneven rim is not a disaster. It does demand a kiln that reaches stoneware temperatures, so check what your local studio fires to before buying a 12.5kg bag. If they only fire to 1140°C, look for a mid-fire stoneware formulated for that range rather than forcing a higher-firing body to underperform.

Porcelain: Beautiful, Brilliant, Occasionally Infuriating

Porcelain is made largely from kaolin, which gives it its bright white colour and, when rolled thin, a lovely translucency. It is also the most demanding of the three. It has a short working range: too dry and it cracks at the slightest pressure, too wet and it slumps. It dries fast, remembers every careless bend, and warps in the kiln if unsupported.

None of that means you should avoid it. It means you should approach it deliberately. Choose a porcelain blended with a little fine grog if you can, which improves its willingness to hold a form. Build small, use slender coils, compress every join with a rib or your thumb, and dry finished pieces slowly under plastic sheeting. Pinch pots, delicate slab dishes, jewellery and lamp bases suit it beautifully. Large coiled pots are possible but will test your patience.

Matching the Clay to the Technique

The same bag of clay can behave very differently depending on how you ask it to move. A rough guide:

• Pinch pots ask for a smooth, plastic body. Earthenware and smooth stoneware are kindest to beginners; porcelain gives the finest walls if you work slowly and keep the walls even.
• Coils need clay that bends without tearing. A moderately plastic stoneware or earthenware is ideal. Heavy grog makes coiling harder, not easier, because it reduces the body's stretch.
• Slabs benefit from grog. A stoneware containing 20 to 30 per cent fine grog resists warping, releases moisture evenly and stays workable at leather-hard stage. Earthenware slabs are fine for flat, decorative work but more brittle.

Grog, Shrinkage and Other Practicalities

Grog is pre-fired clay that has been crushed and added back into the body. It opens the clay up, reduces shrinkage and gives the surface tooth, which helps joins grip. It also makes the clay less plastic, so more grog is not automatically better.

Shrinkage is the detail that catches people out. Porcelain can shrink 12 to 15 per cent from wet to fired; stoneware usually 6 to 10 per cent; earthenware around 5 to 8 per cent. If you are making a lid to fit a jar, or a set of tiles for a specific gap, those centimetres matter. Make a test tile first: mark a 10cm line in the wet clay, fire it, and measure again. Keep the number in your notebook and you will save yourself a great deal of frustration.

Drying is the other quiet killer. Hand-built pieces are thicker and more uneven than thrown ones, so they need slower, more even drying. Wrap work loosely in plastic for the first few days, then turn it regularly so air reaches all sides.

Buying and Testing Without Wasting Money

Buy 5kg of one or two bodies rather than a whole box. Make a few test tiles from each, fire them alongside your normal work, and note how they feel to work, how they dry, how they glaze and what colour they finish. Ask the studio what firing temperature and glazes they use, and buy clay that fits those conditions rather than the other way around. Glaze and clay need to be compatible; a glaze formulated for earthenware will not behave on stoneware.

Once you find a body you trust, buy it in quantity and keep to it for a while. Consistency teaches you more than variety. There is real pleasure in knowing exactly how a clay will respond when your thumb presses into it — and that knowledge is worth more than any label on a bag.