The Glassblowing Process at the Historic Jamestowne Glasshouse
1. Raw materials are mixed together in the proper ratio to form the batch. The main materials are sand, soda ash, pot ash and lime.
2. The batch is put in the furnace and melted to form molten liquid glass. Historic Jamestown's modern, natural gas furnace melts a batch in nine hours at 2350 deg. F.
3. The tips of blowpipes and gathering irons are preheated in the fire until they are slightly glowing.
4. Glass is gathered on the end of a blowpipe by dipping the tip of the pipe into the pool of molten glass and turning the pipe.
5. The glass is rolled on a steel plate called a marver to center it and slightly cool the exterior.
6. Air is blown through the pipe into the glass to expand it and make it hollow.
7. Hand tools, gravity and more air are used to manipulate the shape. The glass is taken back to the fire (a reheating chamber called a glory hole) to re-soften it as many times as needed.
8. Once the basic shape is formed, the piece is transferred to a solid gathering iron called a punty. The punty has hot glass on the tip, which fuses to the bottom of the glass piece. This piece is broken off of the blowpipe.
9. Once the piece is again reheated, the final shaping is done to the part previously attached to the blowpipe.
10. The finished piece is placed in an annealing oven. The oven slowly cools the piece for about 12 hours. This relieves the stress in the glass and prevents it from breaking.
Last updated: March 31, 2012