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不良・失敗
stone
Japanese: ストーン
Unmelted residue or foreign particles. These can serve as the starting point for opacity or cracks.
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"Stones" are particles of unmelted material or foreign matter that remain within the glass. Unmelted raw materials, or contaminants such as refractory materials or sand, can act as nuclei and serve as the starting point for delamination or cracking.
Proper material management and a clean work environment help prevent problems.
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.