色・発色
redox
Japanese: 酸化還元
A reaction in which the valence of ions changes depending on the amount of oxygen in the furnace, causing the color of the same glass to change.
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Redox is a reaction in which the valence of metal ions in glass changes depending on the amount of oxygen in the furnace atmosphere. Even with the same coloring agent, the color differs between the oxidized and reduced states.
For example, copper undergoes the following reactions: Cu²⁺ (blue to green) ⇄ Cu⁺ (colorless) ⇄ Cu⁰ (red), while iron undergoes Fe³⁺ (yellow to brown) ⇄ Fe²⁺ (blue-green). Electric furnaces tend to be relatively oxidizing environments, but localized reduction can occur due to residual organic matter and other factors.
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.