Nurtured Clay

Workshop notes, cone 03 to cone 10

Trimming foot rings: the cheese-hard window and a 4 mm ring

Cone 6 Body Stoneware Level Beginner Time 20 minutes Filed 15 September 2026 By The Kiln Desk

Process parameters · Technique

Clay body
Stoneware
Cone
Cone 6
Temperature
≈ 1222 °C
Difficulty
Beginner
Working time
20 minutes
Published
15 September 2026

Tools

  • Loop tools in two sizes
  • Needle tool for marking the ring height
  • Calipers for checking the 4 mm ring height
  • Rib for smoothing the transition
  • Rubber stamp or a potter's mark tool
  • Damp sponge kept small — a wet sponge adds water to a pot that is drying
  • Chuck or a foam pad for tall forms that will not sit steady

Trimming is where a thrown pot becomes a designed object, and it is also the fastest way to destroy one. Cut too early and the clay smears; cut too late and it chips. The window that works is narrower than most people think — about 90 minutes for a 6 mm stoneware wall — and the foot ring has dimensions that matter: 4 mm tall, 6 to 8 mm wide, and set at 40 percent of the pot diameter.

Cross-section of a 8 cm form: rim 8 cm, belly 8.5 cm, foot 4 cm.
Vessel cross-section — Section drawn to the rim, belly, foot and height recorded for this entry.
H 8 · Ø8 / Ø8.5 / Ø4 cm

Finding the window

Test with a fingernail on the lower wall, not the rim. At leather-hard the nail leaves a faint line with no clay stuck to it. At cheese-hard it leaves a white scratch and the surface feels cool and dry. Below that — still slightly tacky — trimming drags and stretches the wall. Above it — bone dry — the tool chatters and flakes the surface.

In a 20 degree room at 55 percent humidity, a 6 mm stoneware cylinder reaches cheese-hard about four hours after throwing, and stays trimable for roughly 90 minutes before it goes past. Larger forms take longer; a 30 cm planter may take 12 hours.

Centring for the trim

Tap-centre, do not force-centre. With the wheel at 60 rpm, hold the pot lightly between both hands and tap the side with the heel of the palm until it stops moving. A pot that is tapped into place runs true; a pot that is pushed into place is being held by friction and will shift the moment the tool bites.

If the pot will not tap true, it was thrown oval or it has dried unevenly — check the rim against a fixed reference first. Trimming an oval pot produces a foot ring that is thick on one side and missing on the other.

Cutting the ring

Set a caliper to 4 mm and use it to judge the height of the ring, not your eye. Cut the outside of the ring first with a loop tool, working from the base of the wall downward and inward, then clear the waste clay out with a wider loop so it does not pile up against the spinning pot and distort it.

The ring itself should be 6 to 8 mm wide at the base and taper slightly inward toward the top. A ring that is wider at the top than the bottom traps water and makes the pot unstable; a ring that tapers the other way is what potters mean by a well-cut foot.

Signing and finishing

While the pot is still on the wheel and running true, sign or stamp the underside of the foot ring. Stamp before the clay goes past cheese-hard: after that the impression is shallow and fills with glaze.

Then run a damp sponge around the inside of the foot ring to take off the trimming burr, and smooth the transition between the ring and the wall with a rib. A hard 90 degree angle there is a stress riser — pots crack from the foot ring outward far more often than from the wall.

Steps

  1. Test the wall with a fingernail; trim only when the nail leaves a white scratch with no tack.
  2. Tap-centre the pot at 60 rpm on a clean wheel head, using the heel of the palm on the side of the pot.
  3. Set a caliper to 4 mm and mark the ring height on the wall with a needle tool.
  4. Cut the outside of the ring with a loop tool, working downward and inward from the wall base.
  5. Clear the waste clay with a wider loop, keeping the shavings from building up against the pot.
  6. Cut the inside of the ring so it tapers inward toward the top, 6 to 8 mm wide at the base.
  7. Stamp the underside, sponge the burr off, and smooth the ring-to-wall transition with a rib.

Where it goes wrong

  • Trimming at leather-hard because the pot feels firm. It is firm, and it will smear: the clay is still moving under the tool.
  • Force-centring with the hands instead of tapping. The pot shifts the moment the loop tool bites.
  • Cutting a 4 cm wide foot ring on a small pot. Wide rings equal wide instability; 40 percent of the diameter is the ceiling.
  • Leaving trimming shavings in the pot while it spins. They act as a grinding paste against the wall.
Symptom and cause
Symptom Cause
Crack running from the foot ring outward after firing a sharp 90 degree junction between ring and wall concentrated the stress.
Ring is thicker on one side the pot was not running true when it was trimmed, usually because it was thrown oval.
Foot ring chipped trimmed too late, when the clay had passed cheese-hard and became brittle.
Pot rocks after firing the ring base was cut at an angle; check with a caliper and cut flat in one pass.

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

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