Pittsburgh Plate Glass mile-long factory

Pre-Ford plate-glass production: cast onto a metal table, rolled and polished along a mile-long building. Used to set up the productivity contrast with the later float process (50-yard building).

So they poured it on a metal table, spreading it with rollers. This is actually how they made plate glass all the way up until the 1920s. Here's a metal table — they'd melt a vat of glass, pour it onto the metal table, and people with rollers would flatten it out, and then they would polish it to flatten it further, because it would have all kinds of distortion. The rollers wouldn't be perfect, they'd be different thicknesses. Pittsburgh Plate Glass, located in Pittsburgh — there was a building, a mile long, where they would cast the glass at a little facility like this in the 1800s, pouring on a metal table, and it would just move down these roller beds and be polished for a mile. Because it's so brittle, they didn't want to pick it up, particularly when it had these surface flaws. Once it gets polished at the end, then you could ship it. The factory was literally a mile long, just because you want to have the process flow that way.