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How does changing temperature allow molten glass to be shaped by glassblowing?

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Glassblowing relies on the relationship between temperature and the viscosity of glass, an amorphous solid. Unlike crystalline materials that undergo an abrupt phase change at a specific melting point, glass transitions gradually from a rigid solid to a liquid state as it is heated.12

As the temperature of the glass increases, its viscosity decreases significantly. At high temperatures—such as those found in a furnace—the glass reaches a state where it has the consistency of molasses, allowing it to be gathered on a blowpipe and inflated or shaped by hand.345

Specific temperature-dependent viscosity points guide the process:
* Working point: The temperature at which the glass is sufficiently fluid to be delivered to a forming machine or shaped by a glassblower.3
* Softening point: The temperature at which the material begins to slump under its own weight.3

By carefully controlling the heat, a glassblower maintains the material within a workable viscosity range, enabling the creation of complex forms before the glass cools and its atomic configuration becomes fixed.153