色・発色
gold ruby
Japanese: ゴールドルビー
A deep red color produced by gold colloids. The color develops when the temperature is held at around 650°C. / Note: Prolonged exposure to high temperatures causes the color to turn brown.
A deep red produced by gold colloids. The color develops when the temperature is held at around 650°C.
Note: Browning occurs at high temperatures or over long periods of time
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Gold ruby is a deep red color produced by colloidal gold (Au nanoparticles). When the material is reheated (struck) near the slow-cooling point after reaching its maximum temperature, the dispersed gold atoms grow into nanoparticles and emit a red color due to surface plasmon resonance.
Standard conditions involve holding the sample at around 650°C for approximately two and a half hours (120 minutes). If the temperature is too high or the holding time is too long, the particle size increases and the sample turns brown; if the holding time is too short, the colloid does not develop and no color is produced.
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.