G1215U

Recipe (Percentages)

Notes & Instructions

G1215U is a high-MgO, low-expansion transparent glaze formulated to prevent crazing on low-silica porcelain bodies. Due to its low thermal expansion, it is optimized for high-vitrification porcelain; use on stoneware is not recommended, as excessive compression may lead to structural failure or brittleness. The glaze chemistry is sensitive to chrome-tin pink and maroon stains, which will not yield expected results. Application notes: To avoid surface dimpling, ensure a controlled firing schedule rather than a rapid ramp. When comparing sources for MgO, fritted sources (Ferro Frit 3249) provide more predictable melting characteristics than raw mineral sources like talc. Technical data indicates a 2% porosity at 1800°F (982°C), suggesting the glaze begins sealing early in the firing cycle. Bisque firing above 1800°F is required to prevent outgassing-related defects such as pinholing and blistering. For alternative formulations with modified MgO levels or material requirements, refer to G1216L or G1216M.