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High temperature, smooth, medium plastic, vitreous, grey-white firing, refined body for reduction and oxidation porcelainous
P580 is a variation on the classic '25 Porcelain' mix (25% ball clay, kaolin, feldspar, flint). It uses a blend of 33% ball clays
and 17% kaolin to produce a body of greater plasticity. It also has additional bentonite to increase plasticity further to allow
us to fine-tune working properties if needed. P580 maintains excellent drying properties and is well suited to machine production
since it has high leather hard and dry strength compared to porcelains.
While P580 is not quite as white as fine porcelains, it still maintains near zero absorption for functional ware. Thus it is a
material-of-choice compared to porcelains if the fired color is acceptable for your application. However, if you can tolerate a
slightly darker fired color, we recommend H555.
P580 is a smooth and slick fine grained body that throws and dries quite well compared to all-kaolin porcelains. Its ball clay
complement gives it a robust nature that makes it a good choice for machine forming and even hand building. It generates very
little slip during throwing and does not work as well when too soft as do more plastic bodies.
However, P580 is fine grained and thus it cannot be expected to dry and handle as well as a coarser stoneware. If you need to join
sections, be sure to follow good practice (i.e. use slip containing an aggregate like molochite, dry ware evenly, use as much
pressure and lateral movement as possible when joining, make ware with an even cross section).
P580 fires darker than P600 or P570. However, its color is stable across the cone 8-10 range in oxidation and its reduction color
is quite consistent from firing to firing.
P580 is quite mature and vitrified and thus produces a very strong product. Thus you must take precautions to make shapes that
have inherent strength to resist warping (i.e. avoid goblets with flared bases, flared or overhung bowls). Kiln shelves must also
be be flat. You may need to use a little kiln wash or alumina to separate lids and vessels as they can stick during firing.
P580 has a fairly high flint content and is thus easier to fit glazes to than P600.
P580's high strength can be severely compromised if a glaze is under excessive compression or tension. We recommend that you
stress-test a piece of ware using a boiling water:ice water test. Ware should be able to survive several two-minute cycles before
trouble appears. If you need assistance to adjust the thermal expansion of your glazes, please call Plainsman.
If you wish to use slip on your ware, make it from a base of P580 itself if possible.
You can develop a compatible glossy or matte base for this body from our suggested starting point base recipes available on our
Internet web site at http://digitalfire.com/education/glaze/cone10.htm. Information is given on how to fit the glaze to your body
and how to customize it it for colors, opacity, speck, variegation, etc. For slip decoration, be careful to match drying and fired
shrinkage of the slip with the body since low temperatures generate little glass to adhere the slip.
The chart shown was produced from a specimen fired once to cone 10 reduction in the Plainsman lab and tested in an Orton
dilatometer. If you fire to a different temperature, employ different heatup or cooldown rates, or glaze-fire more than once the
thermal expansion in your ware may be different than this chart indicates.
Drying Shrinkage: 5.0-6.0%
Dry Strength: n/a
Water Content: 21.0-22.0%
Drying Factor: C110+
Dry Density: n/a
Sieve Analysis (Tyler mesh):
Cone 8: 6.0-7.0%
Cone 10: 6.5-7.5
Cone 10R: 7.0-8.0
Cone 8: 1.0-2.0%
Cone 10: 0.3-0.8
Cone 10R: 0.0-0.5
||Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX: