Centering is the point where almost everyone gives up on the wheel, and it is almost never a strength problem. It is a wheel-speed problem and a bracing problem. This is the sequence that centres 1 kg of stoneware in about 90 seconds: the speed to use for each of the three phases, where the hands actually go, and how to tell whether the mound is centred before you open it.
H 7 · Ø9 / Ø10.5 / Ø5.5 cm
Three phases, three speeds
Phase one is coning up, at 220 rpm for a 1 kg ball on a 30 cm wheel head. Phase two is pressing the cone back down to a squat mound, at 180 rpm. Phase three is the final settle at 120 to 140 rpm, where you stop pressing and simply hold the mound steady for ten seconds.
Beginners run the wheel too slow because a fast wheel is intimidating. Below about 150 rpm the clay does not have enough momentum to be moved by steady pressure, so you end up fighting it with force — which is exactly when wrists get hurt and mounds go oval.
Where the hands go, and why the elbows matter
Brace both forearms on your thighs, or on the splash pan rim if you throw standing. That converts your hands from levers into rigid stops. The left hand sits at roughly the 7 o'clock position with the heel of the palm on the outside of the mound; the right hand comes over the top at 1 o'clock with the palm heel pressing down and in.
Water is applied to the hands, never poured on the mound. Two or three dips of the fingertips per centering is enough. A mound wetted to the point of shine is already losing its ability to hold a wall, because the outer 3 mm are now slip.
The wobble test
Stop pressing and let the mound spin at 140 rpm. Look at the top edge against a fixed reference — a shelf bracket, the edge of the splash pan, anything that does not move. A centred mound shows a stationary rim of clay with the wheel head turning under it. An off-centre mound shows the rim drifting back and forth through 2 or 3 mm.
Do not open the mound until the wobble test is clean. Every minute spent fighting an off-centre mound later costs ten, because the wall thickness will be uneven all the way up and the rim will rise while wandering.
Fixing a mound that will not centre
If two minutes of steady pressure has not done it, cone it back up to a full cone and start again. That is not failure, it is the standard repair, and it takes 20 seconds. What makes a mound uncatchable is almost always one of three things: the ball was not wedged evenly so it has a hard side; the wheel head is not clean and the clay is skating; or your elbows have come off your thighs.
A fourth cause is clay that is too soft. Below about 17 percent moisture stoneware centres easily; above 22 percent it slumps away from the hands no matter what you do. If the ball leaves slip on your palms the moment you touch it, put it back in the bag and take a firmer piece.
Steps
- Wedge the ball to a uniform cone and slap it down slightly off-centre, pressing it firmly onto a clean, barely damp wheel head.
- Set the wheel to 220 rpm and cone up: left palm heel on the outside, right hand over the top, drawing the mass up into a cone over four or five passes.
- Reduce to 180 rpm and press the cone back down with the right palm heel while the left hand contains the base, so the mass spreads into a squat dome.
- Drop to 120 rpm, take two dips of water, and hold the mound between both hands for ten seconds with no pressing at all.
- Run the wobble test against a fixed reference. If the rim drifts, cone up and repeat.
- Sponge the wheel head clean around the base and check that the mound has no spiral line on top before opening.
- Leave the wheel at 120 to 140 rpm for opening — you will raise it again for pulling, not for this.
Where it goes wrong
- Pouring water over the mound. It wets the clay unevenly and the mound will not hold a pulled wall.
- Letting the elbows come off the thighs. The hands then move with the wobble instead of correcting it.
- Centering under 150 rpm. The mound looks calm but you are moving it with force rather than pressure, and it will not be truly concentric.
- Reaching for a bigger ball before 1 kg centres reliably. The faults are identical at 5 kg, just faster to appear.
| Symptom | Cause |
|---|---|
| Wall rises on one side only | the mound was never fully centred, so one wall starts thicker and rises faster. |
| Spiral ridge on the top of the mound | the right hand is coming over the top faster than the left hand contains the base; slow both down. |
| Clay skating on the wheel head | a wet or gritty wheel head, or a ball that was not pressed down firmly on landing. |
| Palm-shaped depressions in the finished base | too much downward pressure in phase two, which thins the floor before opening begins. |
Recipe and schedule numbers here were recorded on the workshop’s own kiln. A different kiln, a different thermocouple position or a different clay batch will move the result, so treat every firing schedule as a starting point and keep your own log beside it.
Same cone — Cone 6
- Glaze thickness by the numbers: specific gravity, dip seconds and grams per area Stoneware
- Reading a glaze fault: six defects and what actually causes them Stoneware
- Opening and flooring: how thick the base actually needs to be Stoneware
- Rolling slabs to an even 8 mm and joining them so the seam outlives the pot Stoneware
- Spiral wedging a 5 kg batch without trapping air Stoneware
- Throwing a 24 cm cylinder from 1.5 kg: the proportions that keep it standing Stoneware