Plainsman Clays | P700
P700 High Fire Porcelain
$90.80 / 20 kg (44 lb) Pugged
$0
Suggested retail price. In-store prices and availability may vary by location.
High fired, White burning, Smooth, Plastic, Vitreous, Translucent, Porcelain clay body
Specifications
Type
High temperature porcelain · white burning · fully vitreous · translucent
Texture
Smooth and fine grained · plastic
Usage
Throwing · hand building · functional ware · reduction and oxidation firing
Temperature
Cone 9 · 10 · 10R – we recommend cone 10 (cone 10 = 1285 °C / 2345 °F). P700 reaches zero absorption at cone 10 and at cone 10 reduction.
Colour
Translucent white in oxidation · clean blue white at cone 10 reduction
Shrinkage
Dry 5.7–6.2% · fired 7.6–8.1% at cone 9, 8.0–8.6% at cone 10, 8.7–9.0% at cone 10 reduction
Absorption
Cone 9 0.0–0.3% · cone 10 0.0% · cone 10 reduction 0.0%
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
P700 is a high temperature porcelain made for functional ware in both reduction and oxidation. It is smooth and fine grained, with no visible grain in the fired surface, and it comes out of the kiln with a silky finish.
It is the most vitreous of our high fire porcelains. Absorption reaches zero at cone 10 and at cone 10 reduction, which gives a dense, strong, fully matured body, and a thin wall is translucent against a light.
Colour is where P700 separates from the rest of the line. Oxidation gives a translucent white. Cone 10 reduction gives a clean blue white rather than the warmer off white or ivory our other high fire porcelains settle into.
Working properties
- P700 throws and hand builds, and it holds detail and a crisp profile well.
- Dry it slowly and evenly, under cloth and plastic, and give large flat forms such as plates the most time of all.
- Keep the cross section even. A wall that changes thickness through a piece dries at two different rates, which is what opens cracks.
- When joining sections, use a slip with a low water content, apply as much pressure as you can, and move the two surfaces laterally against each other so the slip takes hold.
- Because P700 goes fully vitreous, shapes with little structural strength of their own can move at peak temperature. Straight sided cylinders, goblets with a flared base, and severely overhung or flared bowls are the ones to watch. Fire on a flat, level, kiln washed shelf, and test a form before committing a large run to it.
Fired colour & cone behaviour
- Translucent white in oxidation. Clean blue white at cone 10 reduction.
- At cone 10 and cone 10 reduction absorption is zero. The surface comes out smooth and silky, and thin walls read translucent against a light.
- Fired shrinkage runs higher on P700 than on our stonewares, so allow for it when you size work and when you fit lids and galleries.
Glazes & glaze fit
- The white fired colour does not shift glaze colour, so a glaze reads close to true on this body, and the blue white reduction ground keeps a transparent cool and clean.
- Fit a glaze by testing rather than by calculation. Adjust the glaze, fire it, then thermal stress the piece by taking it from boiling water straight into ice water, and repeat until the glaze comes through the test without crazing.
- A fully vitrified porcelain is strong, but a glaze under tension takes a lot of that strength away. Ware that fits properly comes through several two minute boiling to ice water cycles without crazing or cracking.
- For slips, match the drying and fired shrinkage to the body, and build the slip on a P700 base. P700 shrinks more than most, so the match matters more here.
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