Home | Products | Overview
M390 is very similar in composition to M350 and shares the very fine natural smooth character. It is however more plastic. Its darker color tends to limit it to specialized glaze effects. M390 contains 5 different clays, each of which is quite balanced on its own.
M390 is high in iron and thus burns quite dark as it matures in the kiln. At cone 3-4 it is a very warm toasty red that variegates to a deep red by cone 5. At cone 6 the body darkens to a deep red brown. At cone 7 the color lightens somewhat as the body begins the melting process. We try to maintain the porosity at about 1.75-2.0% at cone 6 to hold onto the red color. If you fire higher than cone 6 some of the red color will be lost.
Because of the very high iron content the fired color progression is volatile (the color change from cone 5 to 6 is more dramatic than expected). We recommend cone 4-5 for the warmest color and cone 6 for the best strength and interaction with glazes. If the dark color is not important consider using M350.
M390 is high in silica and will accept most typical cone 6 glazes without producing crazing. However, crazing is possible on M390 if a glaze is high in sodium (i.e. from soda feldspar or nepheline syenite) or is very low in silica or alumina (little clay or flint). As a general rule, unbalanced glazes containing high feldspar and little kaolin or flint are usually a problem. For functional ware we recommend you check glaze fit using a boiling water:ice water immersion test. Please contact Plainsman if you need help to adjust your glaze.
Although M390 fires to red at cone 4-5, keep in mind that the color will darken considerably under a transparent glaze because the latter fluxes the surface of the clay. If you need a red clear glazed result you will have to work at low fire between cone 06-02.
Drying Shrinkage: 6.0-7.0% Dry Strength: n/a Water Content: 19.5-20.5% Drying Factor: c130 Dry Density: n/a
+65: 0.0-0.2% 65-100: 0.5-1.5 100-150: 4.5-7.5 150-200: 7.0-10.0 200-325: 10.0-15.0
Cone 4: 4.5-5.5% Cone 5: 5.0-6.0 Cone 6: 5.5-6.5 Cone 7: 5.5-6.5
Cone 4: 4.0-5.5% Cone 5: 2.5-3.5 Cone 6: 1.5-2.5 Cone 7: 0.5-1.5
BaO 0.3 CaO 0.3 K2O 2.3 MgO 0.7 Na2O 0.1 TiO2 0.7 Al2O3 16.3 P2O5 0.2 SiO2 68.3 Fe2O3 3.6 MnO 0.0 LOI 7.2%
|Plainsman Clays Ltd.
702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX: 403-527-7508