Why Coil Building Rewards Patience

Coil building is the quietest route to a tall pot. There is no wheel to wrestle with, no bat to lift, just you, a bag of clay and a growing stack of rolled coils. It is also the most forgiving method for anyone working at a kitchen table or in a garden shed, because the pot can be as tall as your arm and no taller than your confidence. The catch is seams. A tall vessel is only as sound as the joins between its coils, and those joins are where most pots fail — either collapsing on the table or cracking in the kiln weeks later. Get the seams right and you can build a metre-high planter or a slender vase with real structural integrity.

Setting Up Clay, Slip and Tools

Before you touch the clay, decide what you are building and how fast it can reasonably dry. A tall form wants a clay body with some tooth — a grogged stoneware is far kinder to beginners than a smooth porcelain. Grog gives the wall grip and reduces the shrinkage shock that opens seams.

• Slip: mix clay crumbs with water until it looks like double cream. Too thin and it soaks the coils; too thick and it sits as a layer instead of fusing.
• Scoring tool: a fork, a cocktail stick or a proper scoring tool. You want a crosshatch of scratches, not a smooth groove.
• Ribs: a wooden modelling tool for the outside, a metal kidney for the inside, and a flexible rubber rib for the final compression.
• Support: a banding wheel if you have one, plus a bat or board you can lift the whole pot on without touching the walls.

Roll coils on a clean, slightly damp surface. Aim for 1–1.5 cm thick for a large vessel, thinner for a delicate one, and keep the length to about a hand-span so you are not fighting a rope of clay that wants to loop and kink.

Scoring and Slipping: The Seam That Holds

This is the step people rush, and it is the one that decides whether your pot survives. Press the coil onto the rim only after you have prepared both surfaces.

Score the top edge of the wall with short, criss-cross strokes, going about 3 mm deep. Score the underside of the coil the same way. Paint slip onto both scored surfaces with a soft brush, then press the coil down firmly and evenly. Do not simply lay it on top — push it into the rim with your thumbs, working around the circle in one direction.

Join the ends of each coil by cutting them on a diagonal, slipping and scoring the two angled faces, and pressing them together so the join sits flush. If the ends butt up squarely, you get a weak vertical crack waiting to happen. Alternate where the join sits on each round, so no two seams line up in a vertical stack.

Blending Every Seam Before the Clay Dries

Once the coil is attached, blend the join immediately, while the clay is still soft and plastic. Run a finger or a wooden tool up the outside, drawing clay from the coil down over the seam, then do the same on the inside. Work in short sections, supporting the wall with your other hand so you are not pushing the form out of shape.

Aim to make the seam invisible, not to flatten the wall. The goal is a continuous thickness where coil and wall have become one material. Follow with a rib — a metal kidney on the inside, a wooden rib on the outside — to compress the clay and align the particles. Compression is what closes the microscopic gaps that slip alone cannot fill.

If the wall starts to feel slimy or the coil squashes under your finger, stop. That is a sign the clay is too wet, and blending further will only weaken it. Let it firm up for twenty minutes under a plastic bag, then return.

Building Height Gradually, Round by Round

Height comes in stages, never in one heroic session. Add two or three coils, blend them, then let the pot rest. Cover it loosely with plastic — a bin bag works well — and leave it until the wall is leather-hard: firm enough to hold its shape when you press it, still cool and slightly damp to the touch.

Only then add the next round. This rhythm does two things. It lets each seam set before the weight above bears down on it, and it gives you a chance to correct lean and thickness as you go. Check the profile with a straight edge or a spirit level against the side; a tall pot that leans at 30 cm will be hopeless at 60 cm.

Keep the rim compressed as you build, and thin the wall slightly as the pot rises, so the top is not heavier than the base. When you stop for the day, wrap the whole vessel well, including the rim, and let it rest overnight. A tall coil pot is a marathon, not a sprint.

Drying, Finishing and Troubleshooting

Drying is where tall vessels reveal whether the seams were honest. Dry slowly and evenly, wrapped in plastic that you peel back a little more each day. Rushing this stage causes the classic S-crack across the base and hairline splits along seams.

• Cracks appearing at a seam: the join was starved of slip or blended too dry. Fill with a coil of soft clay, score, slip and blend again while still damp.
• The wall slumping: the clay is too wet or coils are too thick. Stop, cover and let it stiffen.
• Seams reopening when bone dry: the slip was too thin or the join not compressed. Refine the surface and accept that a small repair may be needed after bisque firing with a little slip.

Once bone dry, smooth the surface with a damp sponge or a fine scraper, refine the rim, and sign the base. Fire slowly through the early stages to let any residual moisture escape. A well-built coil pot, with every seam scored, slipped and blended before the clay dried, will come out of the kiln as one solid piece — ready for a garden border or a corner of the kitchen, holding a plant, some dried stems, or nothing at all.