Tuesday, March 29, 2005

Memories of a Corning Glass Factory:

Many years ago I watched Corelleware being made at Corning. Corelle is a sandwich of three glass layers. It's the tension between the layers that gives Corelleware its strength.

The three-layer glass sandwich forms as the gobs of molten glass come out of their vats and fall together into the first of a series of molds.

I also saw the machine that shaped the handle on the Corelle cups. For the first year they were manufactured, Corelle was sold with the cups from a more expensive line because the Corelle cup handles were not forming properly. The cup started as a flat molten pancake with a flat handle. It was shaped into a cup in a series of molding steps, and then it passed by a station where five little hammers tapped the still-flexible handle to push it into its correct shape. The five taps occurred in less than two seconds. It took Corning engineers a year to figure out the ideal sequence and strength of those taps to shape the handle.

My favorite part of the glass manufacture line was a device called a "motion inverter." The purpose of this device was to turn an item upside down. The motion inverter was simply a round horizontal bar, maybe a half-inch in diameter, across the moving line. A robot-like device would pick up a cup or dish and set it on the motion inverter, just a tiny bit off center. The cup would hang there for a long moment, then fall off while flipping over, down onto the next conveyer belt.

One of the most critical jobs was preventing jams on the first machine that shaped the molten glass. Glass moved through 8 or 12 stations on this machine in less than a minute. A jam here had the potential to shut down the entire line, and it could take six weeks to start the line up again. I was told that good workers on that machine often fell asleep on the job. This was okay as long as they could wake up and clear a jam when the alarm sounded, in just a few seconds.

It took six weeks to start up a glass furnace because the furnaces at that time used electrical radiant heat. To make glass you have to melt sand, and sand is not transparent, so radiant heat will not pass through it. First a special cover was placed on the vat with many incoming gas lines, and a gas fire melted the sand for weeks. Finally the sand was molten and transparent, allowing them to switch to the electrical radiant heat. Then they needed to get the right consistency and they could start manufacturing. More sand could now be slowly added without unduly clouding the interior of the vat.

These giant vats – about ten feet in diameter I think - could withstand the 2000 degree temperatures, but the metal supports that held the vats in place could not. The vats were suspended high above a gigantic unused cellar. If molten glass overflowed the pots, enormous water hoses were aimed at the metal supports to cool them, to try to keep them from melting on contact with the dripping glass.

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