Abbot Suger applied the terminology of gemstones to the “sapphire” blue glass used so abundantly at St. Denis. Ruby red was another vibrant color used in many windows but the craftsmen had the dilemma of how to put the whites in the eyes of a devil such as the ruby demon in St. Ouen in Rouen or to make an intricate white design on a red skirt or to portray very light skin or to show white teeth from behind red lips. Their solution was laminating red and white pieces of glass together (flashing) and then scratching off the red to reveal the white below. This process was called abrading.