M340S Mid Fire Clay
M340S is a light beige, cone 6 clay body with dark speckles running all the way through it. It is the one to reach for if you want a spotted, variegated surface under your glazes.
$37.92 / 20 kg (44 lb) Box
Plainsman Clays | M340
M340 Mid Fire Clay
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$0
Suggested retail price. In-store prices and availability may vary by location.
Mid fired, Buff burning, Plastic, General purpose, Hand-building and Throwing clay body
Specifications
Type
Medium-fired buff burning stoneware · general purpose · vitreous
Texture
Plastic, smooth, with a subtle fine-grained texture
Usage
Throwing and hand-building · general purpose stoneware
Temperature
Cone 5 · 6 · 7 – it is recommended to fire to cone 6 (1222 °C / 2232 °F). Witness cones are encouraged to verify the firing temperature.
Colour
Colour ranges from a straw at cone 4 to a warm buff-grey at cone 6 and 7
Shrinkage
Dry 6.0–7.0% · fired 5.0–5.5% at cone 5, 5.5–6.5% at cone 6, 5.8–6.8% at cone 7
Absorption
Cone 5 1.3–1.8% · cone 6 0.7–1.0% · cone 7 0.3–0.5%
Every figure is a measured range from the Plainsman lab, not a single nominal number. Cone equivalents are Orton self-supporting cones at 108 °F/hr.
Description
M340 is mined locally, using various stoneware clays. It is one of our most popular general-purpose bodies and handles most of what a mid-range studio makes – thrown work, hand-built work, and everything in between.
The particle size distribution is what makes it behave the way it does. The range of sizes gives the clay its dry strength; the coarser size allows water to escape out of the wall structure, so work dries more readily than a dense uniform fine particle body.
Fired, colour ranges from a straw at cone 4 to a warm buff-grey at cone 6 and 7.
Working properties
- A good clay to both throw and hand-build with. It has a plastic, smooth and subtle grained texture to it, and excellent dry strength that comes from the diverse particle size distribution.
- The clay body is fine enough that 95% of a raw sample washes through a 200-mesh sieve without any grinding.
- Take care with larger pieces – flat plates, shallow bowls and sculptural work. Evenness of drying matters more than speed.
Fired colour & cone behaviour
- Colour ranges from a straw at cone 4 to a warm buff-grey at cone 6 and 7.
- Cone 5, 6 and 7 are all within range, and it is recommended to fire to cone 6. Witness cones are encouraged to verify the firing temperature.
Glazes & glaze fit
- M340 is high in silica and will craze fewer glazes than our porcelain bodies. Crazing is still possible with a glaze high in sodium, or one short on silica or alumina – an unbalanced glaze carrying a lot of feldspar and little kaolin or flint is the usual culprit.
- The iron in the body mutes bright glaze colours compared with the same glaze on porcelain. Applying an engobe can help with colour development.
- If you are making functional ware, a boiling water to ice water immersion test will tell you whether the glaze really fits.
Chemical analysis
SiO₂ 69.2 · Al₂O₃ 17.7 · Fe₂O₃ 1.4 · K₂O 2.1 · MgO 1.2 · TiO₂ 0.6 · CaO 0.2 · Na₂O 0.1 · MnO 0.0 · LOI 7.5%
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M340GS Mid Fire Clay
M340GS is M340S with added grog. It has a slightly coarser tooth within a plastic matrix, and is good for work that requires some structural strength. It is made almost exclusively from our native clays – take care not to over-saturate the surface with water.
$37.95 / 20 kg (44 lb) Box
M390 Mid Fire Clay
M390 is a smooth, very plastic red stoneware for functional ware at mid range. It carries more native Redstone than any of our other bodies, which is where the depth of colour comes from, and it is a joy to work with on the wheel.
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