Wedging Clay Properly Before Throwing on the Wheel

Why Wedging Is the Best Ten Minutes You'll Spend

Wedging is the potter's equivalent of kneading dough, and it earns its keep twice over. First, it makes the clay pleasant to throw: an even, homogenous body that responds to your fingers instead of fighting them. Second, it protects the pot long after it leaves the wheel, because the faults wedging removes are the same faults that open up as cracks in the kiln.

The two enemies are air pockets and uneven moisture. A trapped bubble of air can blow out a wall as you pull, or leave a small cavity that becomes an S-crack across the base during drying. Patches of wet and dry clay behave differently under pressure, so the wall you thought was even turns out thick on one side and thin on the other — and the thin side is where the pot will fail. Ten minutes at the wedging board saves you hours of tears at the kiln.

Getting the Clay to the Right Consistency First

Wedging cannot rescue clay that is the wrong wetness. Freshly opened bag clay is usually close, but reclaimed clay needs slaking first. Break it into lumps, lay it on a plaster bat or a length of board covered with old sheeting, and let it dry until it holds together when squeezed. Turn the lumps every few hours so the outsides do not crust over while the centres stay sloppy.

You are looking for a body that is cool to the touch, faintly tacky but not sticky, and that takes a clean thumbprint without your finger sinking in. If it sticks to your hands, it is too wet — spread it out again. If it cracks at the edges when you fold it, it is too dry — dampen and wrap it in a plastic bag overnight. Clay below about 10°C also wedges badly, so bring a cold bag indoors for a few hours before you start.

Spiral Wedging, Step by Step

This is the standard method for throwing clay, and it suits anything up to about 2kg. Work on a canvas-covered board, a plaster bat, or a wooden board you keep specifically for the job — bare absorbent wood will pull water out of the clay and leave it stiff on the outside.

• Set your board at roughly waist height so you can use your body weight rather than your wrists.
• Shape the clay into a rough cone, then lean it towards you at about a 5–10 degree angle.
• Place your left hand on top of the cone to steady it and control the angle.
• Press the heel of your right hand into the base of the cone, pushing down and away at about 45 degrees.
• Fold the clay back over itself, rotate the mass a quarter turn, and repeat.

Aim for a steady rhythm: press, fold, turn. For a 1kg ball, forty to sixty cycles will do it. You will feel the body change — it becomes smoother, more plastic and slightly warmer under your palm. Stop there. Over-wedging drives air back in and stiffens the clay, particularly with stoneware that has a lot of grog.

Ram's Head Wedging for Stiffer Clay and Blends

Ram's head wedging works by shearing the clay in layers rather than folding it, which makes it excellent for large amounts, firmer bodies and blending two clays together. Slam the mass down onto the board, then tear it in half. Pick up one half, slam it down on top of the other, and rotate the whole mass ninety degrees. Tear again, slam again, turn again.

Twenty to thirty repetitions is usually enough. The advantage is speed and the fact that any air present is pressed out in flat layers rather than rolled into bubbles. The disadvantage is noise and the amount of dust and mess it makes, so keep a dedicated board and a damp cloth nearby.

Testing Whether Your Clay Is Really Ready

Do not rely on feel alone. Cut the wedged ball in half with a wire and look at the cut faces.

• Pinholes — fine dark specks mean air is still trapped. Wedge again, more thoroughly.
• Spirals and streaks — a good sign in spiral-wedged clay, provided the body colour is otherwise uniform.
• Colour variation — pale and dark patches mean uneven moisture. Wrap and leave overnight.
• Gritty seams — you are looking at unblended reclaimed clay. Wedge more or blend the batches.

Squeeze a small coil flat between your fingers too. It should stretch without tearing and feel consistent all the way through. Once the clay passes, wrap each wedged ball tightly in plastic and let it rest for an hour or two before throwing — the moisture equalises further, and the clay throws noticeably better for it.

Habits Worth Building

Wedge in batches rather than one ball at a time: five or six balls of the same weight, wrapped and stacked, mean you can sit down at the wheel and work without stopping. Keep your hands damp but not wet, and dry them before handling a fresh ball. Never wedge on a surface that has dried clay dust on it — you will simply press grit into the body.

Label your wrapped balls with the weight and the date. Clay improves with a week or two of rest after wedging, provided it stays sealed. And if a pot does crack in the bisque firing, cut it open before you blame your throwing — nine times out of ten, the evidence will be a bubble or a wet streak sitting exactly where the fault began.