設計・制御
Crash Cool (Stage E)
Japanese: 急速冷却（E段階）
Stage 5 of the firing program. This stage involves rapidly lowering the temperature from the peak temperature to the cooling point (e.g., 482°C). Passing through the decarburization range (600–750°C) quickly prevents decarburization.
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Rapid cooling (Stage E, Crash Cool) is the fifth stage of the eight-stage firing program; it is the phase in which the temperature is rapidly lowered from the peak temperature to the Bullseye-system slow-cooling point (482°C) (§8.1, §8.3). In η-T-t trajectory terminology, this corresponds to “crash.” By passing through the temperature range where opacity nuclei are prone to form (600–750°C, “Zone III” in Chikaoka’s four-zone classification) in the shortest possible time, this phase prevents surface clouding and wrinkling (opacity). After rapid cooling, the glass “freezes” at the slow-cooling point and then transitions to the subsequent stress-relief phase.
The cooling rate during the E stage must balance the need to prevent loss of transparency with glass safety. For standard Bullseye COE90, a rate of approximately 300–480°C/h is typically used, but this rate must be reduced for thicker pieces (Adams-Williamson rule: allowable cooling rate q ∝ 1/thickness²). The key to quality control in fusing lies in minimizing the time spent cycling between the 600–750°C range by combining rapid heating in Stage C with rapid cooling in Stage E. Since the maximum rapid cooling rate achievable depends on the electric kiln’s performance (e.g., whether it can be opened and closed, and whether it has a fan), it is crucial to understand the kiln’s characteristics.
Related Concepts
Peak Temperature Hold (Stage D) (firing-stage-d) · Annealing Soak (Stage F) (firing-stage-f) ・Rapid Cooling (crash-cool)・Bubble Squeeze Zone (bubble-squeeze-zone)・η-T-t Framework (eta-t-t-framework): Understand the overall strategy for preventing loss of transparency and managing distortion in conjunction with these processes.
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.