- Between Ambient – 200°F: Physical water evaporation.
- From 400°F – 1500°F: Organic material (paint, wax, oils) burns off. This often produces smoke—ventilation is important.
- About 660°F: Chemical water evaporation.
- Chemical water is part of the clay’s molecular structure.
- Loss of chemical water permanently changes clay to ceramic, making it no longer recyclable with water.
- Above 1500°F: Sintering.
- Particles fuse under heat (and/or pressure).
- The ceramic becomes harder and more compact.
- Shrinkage occurs, depending on the clay.
- Between 1500°F – 1971°F (Cone 04): Porosity development.
- At this stage, the ceramic is sintered but still porous.
- This porosity allows glaze to penetrate and adhere well during glaze firing.
- Between 500°F – 1500°F: Gasses escape from the glaze.
- Between 1800°F – 2300°F:
- The glaze melts, transforming from a powder to a glass-like surface.
- Exact temperature depends on the glaze.
- Chemical Reactions: Silica, metal oxides, and fluxes melt and react.
- Interface Reactions: The glaze chemically interacts with the ceramic body, affecting glaze color.
- 1940°F – 2269°F: Vitrification of the clay body.
- Clay becomes fully vitrified (glass-like, non-porous).
- Higher temperatures = more complete vitrification.
- Our kilns fire to Cone 6.
- Molten glaze solidifies: Crystallization may occur, affecting appearance. Controlled cooling impacts crystal formation.
- Shrinkage: Both glaze and ceramic shrink. Different rates may cause cracks in the glaze (crazing).
¶ Before Firing: Maintenance & Troubleshooting