Item #: SIOSWBK
Sio-2 PRNI Black Stoneware with Impalpable Grog.
Sold in 27.5lb bags
Black stoneware clay body with 40% impalpable grog (up to 80 Mesh). Formulated for artistic ceramics, it is ideal for wheel-throwing and modeling smooth pieces with fine details. The high content of grog confers an excellent behavior during drying and firing. Its beautiful and intense black firing color in oxidizing atmosphere is very exclusive of PRN range and becomes an ideal artistic mean of expression. In reducing atmosphere, metallic effects with shades of blue are obtained. Suitable for tableware (food-safe), according to ISO 6486:1999. Available in extruded body (moist form).
Recommendations for use with glazes
Use zinc-free (Zn-free) glazes to prevent from unexpected reactions such as bubbling or color changes. Other elements that can react are zirconium (Zr) and tin (Sn). We recommend consulting your usual glaze supplier to ensure proper suitability with this ceramic clay body.
Do not use glazes with a low coefficient of thermal expansion (a25-300ºC <60x10-7ºC-1). The PRN clay fired at high temperature has a high coefficient of thermal expansion in the range of 100 to 200ºC, which causes tensions between the glaze and the support, mainly in pieces glazed on one side only, which can cause breakage during cooling in the kiln or even later (for example, when pouring hot water inside). Check with your usual glaze supplier to ensure that you use glazes with a medium-high coefficient of thermal expansion (a25-300ºC >60x10-7ºC-1).
Firing - Ceramic kiln high fire
Weight/Volume - 27.5 lbs - 12.5 kg
Grog - Impalpable grog
State - Moist form (plastic body)
Stiffness - For wheel throwing and handbuilding
Firing range: Cone 5-6 (2192-22264ºF / 1200-1240ºC)
Bisque firing temperature: Cone 06 (1832ºF / 1000ºC)
Water content: 21%
Plasticity (IP Atterberg): 22
Carbonate content (CaCO3): 0%
Drying shrinkage: 7.0%
Firing shrinkage (1240ºC): 7.1%
Porosity (water absorption at 1240ºC): 1.3%
Dry bending strength: 4.6 N/mm2
Fired bending strength (1240ºC): 33.3 N/mm2
Thermal coefficient (a25-500ºC): 51.1x10^-7ºC^-1