温度・粘度
Flow/Cast Zone
Japanese: 流動・キャスト域
The temperature range of 810–870°C. This is the temperature range at which glass flows into the mold as a liquid. This allows for processes such as lost-wax casting and box casting, enabling the glass to flow into the fine details of the mold.
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The Flow/Cast Zone is the temperature range from 810 to 870°C, during which the glass flows as a fluid into the refractory plaster mold (§10.2). This corresponds to a viscosity range of log η 4–5 (Pa·s), at which the glass is able to flow into the finest details of the mold due to gravity and pressure differences. Casting techniques such as lost-wax casting (815–870°C), box casting (815–840°C), and gaffer flow into fine details (850–900°C) utilize this temperature range.
The flow of the material into the glass mold is rate-limited by viscosity η and surface tension γ, and the flow depth h is of the order of √(γt cosθ/η) (§10.3, Kucuk 1999). Although flow progresses as viscosity is reduced at higher temperatures or as the holding time is extended, this is counterbalanced by the risk of prolonged residence in the devitrification zone. Gaffer Casting Crystal (which contains lead and has a viscosity curve shifted toward lower temperatures) achieves lower viscosity within the same temperature range, which is why it flows more easily into complex molds. Preheating (predrying) the plaster mold to remove moisture from the mold before the main firing is a prerequisite for safe firing.
Related Concepts
Block-Press Zone · Pot-Melt Zone ・Refractory plaster, predry (preheating of plaster molds), and Gaffer Casting Crystal—understand the temperature design for the casting process in conjunction with these elements.
This entry is written in Japanese by Rei Chikaoka and translated for readers outside Japan. If something reads oddly, the original is the source of truth.