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P600's recipe is such that if we experience variations in the raw materials, the body is more dramatically affected than others. It requires close supervision and adjustment on our part to maintain its fired properties. Occasional variations in kaolin have forced us to add some ball clay to the recipe at times (resulting in slightly darker firing).
However since it is lacking the particle size distribution of more traditional white stonewares it demands more than the usual attention during drying, especially on difficult shapes (like large flat plates). Time is required to remove all the water since the bentonite acts as a barrier to its passage. If you need to join sections, be sure to follow good practice (i.e. use slip containing a clean aggregate grog (like molochite), use as much pressure and lateral movement as possible when joining, dry pieces evenly, avoid making ware with an uneven cross section.
Although P600 is not a true translucent porcelain, it does vitrify to a very pleasant silky surface and does display a measure of translucency on thin pieces. P600 normally reaches zero absorption at cone 10 and 10R. If ware made from it has a shape that is not structurally strong (i.e. a straight sided cylinder, goblets with flared bases, overhung bowls) it is likely to warp, especially if set on kiln shelves that are not flat.
P600 has a more pleasant vitreous surface than H570 and fires whiter but it is more prone to warping during firing. P700, on the other hand, is whiter than P600 and even more vitreous.
In addition, this body fires to a high strength, a strength that can be severely compromised if a glaze is under excessive 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 P600 for the best possible drying shrinkage/fired shrinkage match.
Drying Shrinkage: 5.0-6.0% Dry Strength: n/a Water Content: 22.0-23.0% Drying Factor: C110-C120 Dry Density: n/a
+100: 0.0-0.1% 100-150: 0.1-0.3 150-200: 0.2-0.8 200-325: 3.0-5.0
Cone 8: 7.0-8.0% Cone 10: 7.0-8.0 Cone 10R: 7.5-8.5
Cone 8: 1.0-2.0% Cone 10: 0.0-0.5 Cone 10R: 0.0
|Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX: 403-527-7508