How to Make Medieval Glass
- 1). Start with a small, measured amount of pure sand -- roughly 77 grams. This small amount of glass is best for test-runs and those new to glassmaking, and can be proportionally increased along with the other ingredients to make larger batches of glass.
- 2). Add 15 grams of soda and thoroughly mix it into the sand. According to the Corning Museum of Glass, soda was used to reduce the temperature at which the sand melts.
- 3). Add 8 grams of lime to the mixture. According to the Corning Museum, lime stabilizes the glass, though most early glassmakers were unaware of this property. In many cases, lime simply existed in the small seashells and impurities that were found mixed in the sand used to make glass.
- 4). Pour the mixture into an iron dish. Set the iron dish into a melting furnace. At 1000 degrees Celsius, it will take a day and a half for the mixture to melt. Agitate and stir it frequently with a small iron paddle.
- 5). Pour the melted mixture into another small, cold iron dish. The glass will cool quickly, but will also usually crack.
- 6). Lower the temperature of the furnace to 500 degrees Celsius and put the glass and its second container into it. This step is called refining and is done to achieve a clearer, more uniform plate of glass. Over 12 hours, gently stir the glass to remove bubbles.
- 7). Remove the dish and let it cool, or if desired, pour the glass into a mold of the desired shape. Allow the glass to cool as slowly as possible; this is a process called annealing that allows it to properly harden.
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