How It Works: Corning’s Fusion Process

Flat glass

Science of Glass: How It Works

Science of Glass: How It Works

How It Works: Corning’s Fusion Process

How It Works: Corning’s Fusion Process

Revolutionary technique makes possible the full suite of high performance flat glasses

Corning was the first manufacturer in the world to form specialty glass suspended in mid-air. It's the hallmark feature of the proprietary "fusion" process, a big key to Corning's innovation success over the past two decades.

Here's a quick breakdown on how the process works and why it's so important for Corning.

Raw materials – pure sand combined with other inorganic materials – flow into a large melting tank heated to temperatures well above 1,000 degrees Celsius. The molten glass is homogenized and conditioned before it is released into a large collection trough with a V-shaped bottom, known as an isopipe. The isopipe is carefully heated to manage the viscosity of the mixture and ensure uniform flow.

Molten glass flows evenly over the top edges of the isopipe, forming two thin, sheet-like streams along the outer surfaces. The two sheets meet at the V-shaped bottom point of the isopipe and fuse into a single sheet.

The sheet, still attached to the bottom of the isopipe, then feeds into drawing equipment as it lengthens and begins to cool in midair. Precise control of fusion process conditions impact key product attributes like glass thickness– which could be as thick as one or more millimeters in the case of Corning® Gorilla® Glass 4, or as thin as 100 microns with Corning® Willow® Glass.

The sheet is carefully cooled and stabilized until it reaches the bottom of the draw, where it is cut and moved to a nearby area to complete processing and packaging.

Unlike glass formed by other processes – like the float method, in which hot molten glass flows onto a bath of hot tin – fusion-formed glass can forgo costly surface polishing and many other post-production steps.

But that's just one of the benefits of Corning's fusion process. The glass is remarkably flat, uniform in thickness, and able to withstand heat-intensive processes like application of LCD circuitry. Corning teams scale the fusion process up or down to meet different customers' size and specification requirements.

The fusion process also adds to the toughness of materials like Gorilla Glass and Willow Glass. Breaks and cracks tend to generate from flaws on the glass surface. Even something as small as a microscopic scratch or chip can turn into a crack and cause breakage. Fusion-formed glass and its pristine surface is free of forming flaws and defects.

Fusion-drawn glass is particularly well-suited to the ion-exchange chemical strengthening process that has made Gorilla Glass the standard in tough electronic device covers.

Corning's entire precision flat-glass portfolio – Gorilla Glass, Willow Glass, Corning® EAGLE XG® Slim, Corning Lotus™ Glass, and Corning Iris™ Glass – reflects the constant innovation that has gone into the fusion process since the 1960s.