Red Glass Coloration

The predominantly used red glass pigment today is based on Cadmium, an element hazardous to the environment and toxic to humans. Two possible alternatives are glasses coloured by copper or gold, but there are several problems with their industrial production. The aim of this work has been to obtain a better understanding of gold and copper rubies, and also to investigate other combinations of elements. The impact of different reducing agents on the copper and gold ruby pigments was examined and the colour development in copper ruby glasses was studied extensively. Experimental results provided good evidence that the colour in copper rubies originates from nanoparticles of metallic copper. Both gold and copper rubies are more environmentally friendly than the cadmium based pigment, and must be regarded as possible alternatives. Regarding other alternatives the possibility to combine red colour and semi-transparent alabaster glasses was studied. It was also found that by combining molybdenum and selenium in alkali-lime-silica glass under reducing conditions, a red pigment can be obtained. Red glass originating from this combination has not been reported earlier.