Hot, Hot, HOT!

If you’ve ever toured a float glass facility then perhaps you already know to what I’m referring. A few weeks ago I had just such an opportunity, when Rob Struble, marketing communications manager of Pittsburgh-based PPG Industries, was kind enough to invite members of our editorial staff to tour PPG’s float facility in Carlisle, Pa. What made the tour particularly tempting was the fact that the facility, which houses two side-by-side float lines, was undergoing repairs to one of its lines. The once-in-12-years opportunity, as Rob pointed out, allowed our small group to view a line in action—as well as an up-close view of the inside of a typical line.

We started our tour from the end of the float line, which provided an interesting perspective. We walked quickly past the cutting and sorting lines and into the last chamber of the float line.

“You think that’s hot?” our guide, Mike Henry, asked as he led us into the long room. There wasn’t much to see at that end of the line where the lengthy lehr enclosed the glass being annealed. We learned later that at this point the glass is cooled to about 300 degrees Fahrenheit. Yet sweat beaded on our collective brows and one cardigan was shrugged off as we nodded.

Mike smiled and replied, “That’s not hot.”

We followed our guides further down the line and crossed into the area where the glass actually begins to take its shape atop the molten tin bath. We could see purple licks of flame at the point where the glass was pulled into the lehr. Adjustable wheels on either side of the ribbon essentially pulled the glass out into the desired thickness, one point of the process that determines whether the glass will be a 1/8- or 1/4-inch lite, for example.

“You think that’s hot, don’t you?” Mike joked again.

I personally felt like I’d been vacuum-sealed and stuck in an unvented attic like a pile of discarded winter clothes in July. It became difficult to stop thinking, no, fantasizing about the pack of water bottles sitting in the van. We nodded.

Mike laughed. “That’s not hot.”

Finally we passed the 36-foot-tall regenerators, chambers on either side of the furnace that alternately force hot air into the furnace and take the excess heat back for reuse. We’d reached the end of the line, where batch ingredients were fed into the furnace. As the raw materials were deposited into the open end of the furnace, what was a moment before solid silica, limestone, soda ash, dolomite and cullet now bobbed in a liquid state. Now that was hot—but it was all we could do to stay away at that point.

And of course it’s hot. The peak temperature inside the actual furnace is 3,000 degrees Fahrenheit, the temperature at which silica melts. With the green focus of the upcoming November issue of USGlass on my mind, I couldn’t help but consider how much energy must be required to maintain such high temperatures 24 hours a day.

After a moment’s breath of fresh air outside, where we gazed upon mountains of glistening glass shards, divided by tint and type to be recycled as cullet, our group went back in better prepared for the heat. Our guides then dove into explaining each step of the process and helping us to find the best view of the molten batch as it proceeded through the furnace, into the refiner, along the tin bath, inside of the lehr and finally out into the open where it was cut to size.

On the walk back past the furnace we had more opportunities to peek inside the inner workings of the furnace—and into the interior of the non-working furnace, which is in the process of being rebuilt. We were given a glance inside the refiner, and were able to make out examples of the bubbles removed during the process. At that point Mike also pointed out the “tweel,” a gate that that is adjusted to control the amount of glass that enters the next chamber, the first step in controlling the size of the glass.

We were also given a few moments’ reprieve in two different examples of the air-conditioned control consoles, from which the line’s attendants view the glass via video monitors as it progresses along the line.

While it may differ for my coworkers (pictured here from left: assistant editor Katie Hodge, DWM editor Tara Taffera, yours truly, AGRR editor Penny Stacey and Window Film editor Drew Vass), one of the most interesting parts for me was when we returned to the cutting line where we had first began our tour, but now with the consideration that until the lites were scored and cut, we’d been following the path of one tremendously long piece of glass. As many times as I’d read it, it was mind-boggling to think that the ribbon of glass keeps moving nonstop for years.

CLICK HERE to read Tara's perspective on the trip and HERE to read Penny's recollections of our adventure.

And if you’re interested in seeing this process for yourself—let your glass supplier know you’re interested—or you can take a look at this video from the Glass Association of North America’s Flat Glass Manufacturing Division.