Kinetic Investigation on the Color Striking of Gold Ruby Glass

Gold ruby glass of recipes 71SiO2, 11CaO, 11Na2O, 1PbO, 6K2O (in wt. %) were melted in alumina crucibles at 1500 °C for 2 h with SeO2 (0-200 ppm) and C (0.1-0.25 wt %) as reducing agents and gold (in flaky form) at 200 ppm as a colorant. Clear glass samples were annealed at 570 °C for 30 minutes. The kinetics of striking mechanism were studied by a UV-Vis spectrophotometer accompanied with a heating stage in order to determine a precise annealing and heat treatment schedule, and to increase the uniformity of the red colour in glass. The glass specimens were heated at 625 °C, 650 °C and 700 °C for 5 – 300 minutes respectively. The investigations on an absorption peak appeared close to the typical ruby colour absorption (530 nm) presented the self-striking capability. Results showed that the potential self-striking glass contained 200 ppm of Au0, 100 ppm of SeO2, and 0.20 in wt % of C. The appropriate striking temperature was at 650 °C, and the threshold of the soaking time was 270 minutes.