Corning float glass dual-surface manufacturing

That computer right there has a glass screen. That screen is made — and I can only tell you a little bit about this because I had to sign a confidentiality agreement to go through this plant — but it's made by the float glass process, and the furnace is actually no bigger than this room. It's not anywhere near as wide. They pull out strips of glass from the melting furnace. So it's got the air surface and the tin surface, and then they split it in two and they drop it and reweld it basically by putting the two hot pieces so the two tin surfaces are welded together on the inside. Two pieces of bread coming together with no peanut butter in the middle. Now you have a float glass surface on each surface — each free surface is now a float glass surface. That's how they make something very thin. As it falls by gravity for several stories, it's falling through furnaces that control the temperature so it just slowly thins down and stretches out like Silly Putty. They end up with something that's only fifteen or twenty thousandths thick but has two air surfaces of float glass.

Tom under NDA. Corning's display glass uses both float surfaces as air-side (no tin-side imperfections) plus a protective coating, enabling thin display glass for liquid crystal displays. Layered with indium tin oxide electrodes, polarizing filters, nematic crystals. Closes with Corning's "*Innovator's Dilemma*–anticipating" strategy of selling off mature product lines.

Touchscreen glass needs float-quality surfaces on both sides because the tin-bath side has nano-scale flatness defects that fail under humidity attack. Corning's solution (which Tom is under NDA about) involves welding two float-glass sheets together, burying the tin surfaces inside.

But what about the glass? The glass is 0.3 millimeters thick — twelve thousandths of an inch — and you can get it in sheets 1.8 meters by 1.6 meters wide. You can do big-screen TVs, laminate it with all this other stuff, and that gives it some strength. But glass can become brittle within hours by being attacked by humidity. In the float glass process, the top air surface — where it just uses gravity and air to give you a flat surface — gives you an extremely pure flat surface, and if they use the right composition glass it won't be attacked by moisture. But the side on the tin bath — although they keep the tin bath from oxidizing, you shouldn't have big defects — if you go in there with an atomic force microscope and measure the flatness, the tin side is nowhere near as flat and as perfect as the air side.