During the 18th century Bohemian glassmakers discovered chalk glass and it replaced the thin and fragile Cristallo Glass from Venice. The thick-walled, clear crystal glass was perfectly suited for glass overlaid with colour that had just come into fashion and likewise for the glass-finishing techniques of cutting and polishing. The high level of light refraction and brilliance of the glass was the perfect representational medium for European courts to demonstrate their power and splendour.
The creation of a red translucent glass was especially coveted since glass production began and glassmakers adopted the red ruby „carbuncle,“ as their role model. Albertus Magnus, who lived in the 13th century, regarded it as the most precious stone of all, because its power was „similar to that of the sun and the stone was even capable of glowing like coal in the dark.“
The difficulty in producing red glass lay in the exact composition of the glass mass and the control of the fire during initial processing. In Potsdam around 1680 the famous glassmaker Johann Kunckel was able to smelt a red glass that contained gold – the needless to say – valuable, cranberry, or gold ruby glass. This glass is an absolute rarity even today because so few glass foundries were capable of producing cranberry glass and the few examples that still exist are extremely valuable.
If colourless glass is re-heated, only 0.03 per cent of gold is required to turn it into a crimson-red translucent glass, by the way.