Nurtured Clay

Workshop notes, cone 03 to cone 10

Throwing plates off the hump: no trimming, no warping

Cone 6 Body Stoneware Level Intermediate Time 25 minutes Filed 17 October 2026 By The Kiln Desk

Process parameters · Technique

Clay body
Stoneware
Cone
Cone 6
Temperature
≈ 1222 °C
Difficulty
Intermediate
Working time
25 minutes
Published
17 October 2026

Tools

  • Cutting wire with two handles
  • Needle tool for the outer edge
  • Hard rubber rib for compressing
  • Two boards or plaster bats for weighted drying
  • A 2 kg weight — bricks or a bag of clay
  • Chamois leather for the rim
  • Metal kidney for smoothing the underside after cutting free

A plate thrown flat on a bat needs trimming, and trimming a wide flat disc is where warping starts. Throwing off the hump removes the step entirely: you shape the underside of the rim as you go, cut the plate free with a wire, and the foot is already formed. It is faster, it wastes less clay, and it produces a flatter plate than any trimmed one.

Cross-section of a 3.5 cm form: rim 26 cm, belly 24 cm, foot 10 cm.
Vessel cross-section — Section drawn to the rim, belly, foot and height recorded for this entry.
H 3.5 · Ø26 / Ø24 / Ø10 cm

Building the hump

Start with 4 to 5 kg of stoneware centred on the wheel head into a dome about 12 cm tall and 20 cm across at the base, tapering to 6 cm at the top. Wedge it properly — a hump with air pockets throws every plate off it. Compress the top surface with a rib and let the hump stiffen for 20 minutes before the first plate; a freshly centred hump is too soft to support a plate being pressed down onto it.

The hump is reusable for 15 to 20 plates in a session. Rewet only the very top with a sponge between plates, never the sides.

Opening on the hump

Set the wheel to 160 rpm. Press the thumb of the right hand into the centre of the hump top and open a disc 8 cm wide, keeping the left hand flat on the side of the hump for stability. Compress the disc with a rib from the centre outward.

Then work outward with the outside of the right thumb and the inside of the left index finger, taking the disc from 8 cm to 26 cm in four passes, thinning from 12 mm to 7 mm. The plate edge should be 5 mm and the centre 8 mm, so the plate has a slight dish rather than being flat like a coin — a perfectly flat plate warps, a dished one does not.

Cutting free and finishing the rim

Run a needle tool around the plate edge to define a clean 26 cm circle, chamois the rim, then lay a bat over the plate and flip the whole assembly. Cut the plate free from the hump with a wire held flat against the bat, working from the far edge toward yourself so the plate does not slide.

The underside is now flat and ready. If you want a foot ring, press one in with a small rib before flipping — 10 cm diameter, 3 mm deep — but for a serving plate a slightly concave underside with no foot ring is more stable and stacks better.

Drying flat

Plates must dry between two boards, weighted. Lay the plate on a sheet of newspaper on a board, put another sheet of newspaper and a second board on top, and add 2 kg of weight — a couple of bricks or a bag of clay. The weight is what keeps the rim from lifting as the plate shrinks, and it costs nothing.

Turn the stack over after 12 hours so both faces dry at the same rate, and leave it for another 12. An unweighted plate is usually warped by 2 to 4 mm across 26 cm, which is visible in use; a weighted one comes out within 1 mm.

Steps

  1. Centre 4 to 5 kg of stoneware into a dome 12 cm tall and 20 cm across at the base, tapering to 6 cm at the top.
  2. Compress the top surface with a rib and let the hump stiffen for 20 minutes.
  3. At 160 rpm, open an 8 cm disc in the top with the right thumb, left hand flat on the hump side.
  4. Compress the disc, then widen it to 26 cm in four passes with the right thumb outside and the left index finger inside, thinning from 12 mm to 7 mm.
  5. Shape the rim to 5 mm, keeping the centre at 8 mm so the plate carries a shallow dish.
  6. Trim the outer edge with a needle tool, chamois the rim, lay a bat on top and flip the assembly.
  7. Cut the plate free with a wire flat against the bat, then dry it between two weighted boards, turning after 12 hours.

Where it goes wrong

  • Throwing off a freshly centred hump. It compresses under the plate and the plate comes out dished.
  • Cutting free with the wire at an angle. The plate edge becomes bevel-edged and the underside is no longer flat.
  • Skipping the weights during drying. A plate dried flat but unweighted lifts at the rim by 2 to 4 mm.
  • Making the plate perfectly flat. Flat plates and flat floors warp; a 3 mm dish across 26 cm is structural.
Symptom and cause
Symptom Cause
Plate warped after firing with the rim lifted dried without weight; the rim shrank before the centre set.
Plate cracked across the centre during drying the middle was left thicker than 10 mm, so it shrank later than the rim and split.
Underside is not flat the cut-free wire was not held parallel to the bat.
Rim is wavy when seen edge-on the plate was widened too fast in the third pass, so the clay moved unevenly around the circumference.

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

← All Techniques