Page 30: Jason Klein

Next I turned to my friend, Jason Klein, a glass blower who also shares a passion for middle ages reenactment. He graciously volunteered his time and worked with me to produce some tests. 

He melted a commercially-produced clear cullet in his furnace but he was able to come very close to the color of the medieval glass using copper red frit from Zimmerman and approximated the structure by varying his gathering technique allowing the glass to twist in on itself, and folding it multiple times. 

Medieval red (left) Jason's glass (right)

Medieval red (left) Jason's glass (right)

Although Jason was able to produce some impressive results, there is no indication that Saint, the Bryn Athyn craftsmen or their medieval counterparts produced the striated effect in this manner. Rather, Saint’s own research indicates that the medieval glass was streaky within the crucible caused by the addition of copper scales. In all probability it was not made intentionally to be streaky but was striated by nature. Saint, however, intentionally produced a streaky glass by stirring two pots together in his furnace. He even records the reluctance of his gaffer to follow his instruction to stir the pot 100 times! A discussion I had with glassblower and formulator, Peter VanderLaan, confirmed this nature of copper reds. The colloidal suspension they form would tend to create streaks within the glass. I observed another difference. The fritted glass Jason worked with achieved a full red color in his electric annealing oven, whereas both the Saint and the Bryn Athyn records indicate their reds needed a second firing in a reduction atmosphere to reach full color. Working with a skilled glassblower definitely provided the opportunity to make at least a small quantity of striated red that was a very close match to a medieval red.