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The Window Machines: Sheet & Plate Glass

The Window Machines: Sheet & Plate Glass

The mighty glowing columns that stand like pillars in a ghostly cathedral...
    -Anonymous

updraw window-making machine

At the beginning of the 20th century, there was no way to mass-produce flat glass. Although glass cylinders could be drawn by machine, they had to be opened and flattened by hand. What was needed was a way to form sheets of glass directly and continuously.

In 1901, Belgian glassmaker Emile Fourcault invented a machine that drew a glass sheet five stories straight up from a vat of molten glass. Now, sheet glass could be made more easily, but Fourcault’s process marred its surface.

Sheet glass was good enough for most windows, but not for windshields. It distorted the view. Windshields required higher-quality plate glass, ground and polished to remove surface flaws. Making plate glass by hand was too slow to meet the growing demand for windshields.

By 1937, British glassmaker Pilkington Brothers had combined innovations with Ford Motor Company to develop a fully mechanized process for making plate glass. Twin-grinding was an engineering marvel, but the cost in energy and wasted glass was enormous. Rollers squeezed molten glass into a ribbon that was ground on both sides at once, then polished. The machinery stretched out over 1,400 feet (427 meters)—longer than the Queen Mary, then the largest ship afloat.

Bigger Cylinders

As long as glass cylinders were made by hand, their size was limited. Blowing a bigger glass bubble wasn’t the answer. The glass would be too heavy to lift, too heavy to swing and elongate.

American glassworker John Lubbers found a way to make bigger window glass in 1902: he used a machine to draw a cylinder directly from a pot of molten glass. A circular bait, attached to a massive blowpipe, was lowered into the pot, then slowly raised. The glass followed, emerging as a spectacular cylinder that was ten times the size of a handmade one.

Published on October 31, 2011