In creating pure and tough specialty glass, Corning innovators are masters of viscosity.
You can visualize one of the most important scientific concepts in glassmaking by considering something that’s probably in your kitchen cupboard right now.
Open a jar of honey or molasses and observe its thick, semifluid state. Tip it, and – at least at room temperature -- it doesn’t pour quickly. In scientific terms, it’s resistant to flow.
And as it makes its way somewhat reluctantly over the edge of the jar, it’s easy to imagine the internal friction building up at the molecular level within the thick, sticky mass.
Scientists measure that friction in terms of viscosity. The unit of measure is known as a poise – named for 19th-century French physicist Jean Leonard Poiseuille, who developed breakthrough studies of how human blood flows through veins.
When a fluid exhibits a lot of resistance to flow, the viscosity is high. Honey, for example, may have viscosity of about 10,000 centipoise (100 poise) at room temperature.
When a material flows freely, though, there’s very little internal friction and therefore a much lower viscosity. Water has a viscosity of about 1 centipoise at 70 degrees.