Text, Photography, and Diagrams by Bob Leatherbarrow

Between room temperature and 1000°F, glass behaves mainly as a brittle material that breaks when subjected to stresses that are greater than the strength of the glass. Above 1000°F, the glass behaves as a ductile material that bends at lower temperatures and melts together at higher temperatures. Once the glass has successfully entered the ductile zone, the focus shifts to getting the best visual outcome possible.

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