How does glass viscosity make continuous industrial glass production possible?

Viscosity is the fundamental property that enables continuous industrial glass production by allowing the material to transition predictably between liquid and solid states.1

In the manufacturing process, glass is delivered to forming machines at a specific working point, defined by a viscosity of approximately ${10}^4$ poise. At this level, the molten glass is manageable and can be shaped into products like containers or flat glass.12

Continuous production is made possible because manufacturers can extract heat in a highly controlled manner, causing the glass to transition from a workable liquid to a near-solid condition. As the glass cools, its viscosity increases through critical reference points—such as the softening point (${10}^{7.65}$ poise), the annealing point (${10}^{13}$ poise), and the strain point (${10}^{14.5}$ poise)—allowing it to maintain its formed shape while moving through the production line. Because viscosity is temperature-dependent, precise thermal regulation ensures the glass remains consistent throughout these stages.123