The rise of Bohemian glass began in the latter half of the seventeenth century, with the development of potash-lime crystal glass, which has a high index of refraction, and thus is brilliant. Engraving techniques that highlighted crystal's resonance with glass evolved, and ancient techniques that made effective use of its transparency were revived. A prime example of that revival was gold sandwich glass, in which motifs of gold leaf are sandwiched between two fused layers of glass. The central motif on the allegorical scene on this goblet shows St. Nicholas and St. Mary Magdalene supporting the sacret heart each other. Its role was to stand b y true piety.