Mechanism of Red Colour Formation in Photosensitive and Normal Copper-Ruby Glasses

Absorption spectra relating to the photosensitive copper-ruby and normal copper-ruby glasses revealed a strong absorption band at 560 mμ. The shapes of the absorption curves for the photosensitive copper-ruby and normal copper-ruby glasses were almost similar. Electron microscopic study also revealed the presence of the particles of colloidal copper in the size range of 20–60 mμ both in photosensitive as well as in the normal copper-ruby glasses. The results obtained showed that the red colour formation in copper-ruby glasses was due to the presence of the particles of colloidal copper, and not due to the particles of colloidal Cu2O.