Hot glass. Ice-cold water. Watch what happens.

At SCHOTT, we love pushing our glass to the limits. Recently, we gave incredibly hot glass an ice bath, just to see if it would crack. The set-up was simple: An annealing oven, a bucket of ice water, and some sheets of glassceramic. Would the glass-ceramic crack when its temperature plummeted by 1,400° F (760° C) in the span of just a few seconds?

Our first test case: Soda-lime glass

First, we tested a piece of ordinary soda-lime glass, the type of glass in your bedroom windows or that makes up the beer bottles in your fridge. After heating it to nearly 600° F (315° C) in an annealing oven, we dipped the soda-lime glass in a bucket of ice water that registered at just 50° F (10° C). That ordinary glass couldn’t take that rapid drop in temperature, causing it to crack in hundreds of places. So what did we do next? We turned up the heat and tried the same test on glass-ceramics.

Next up in the oven: glass-ceramics

The next test subjects were three pieces of SCHOTT’s NEXTREMA glass-ceramic. Cranking up the heat to nearly 1,500° F (815° C),
we roasted three pieces of NEXTREMA in the oven. These sheets of glass-ceramic look different – we used transparent, translucent, and opaque versions — but all were identical in chemical structure and properties. When the temperature was right, we removed each piece from the oven and immediately dipped it in the frigid water, again at 50° F (10° C). That means the glass went from a scorching 1,470° F (800°C) oven to the icy bath — a difference of more than 1,400° F (760° C). It was sure to crack, right?

In residential uses like grills and toasters, and even in industrial furnaces, we test glass-ceramics often to ensure they withstand extreme heat changes without fracturing. Our tests show that NEXTREMA holds up to even the most extreme scenarios. So have no fear turning your grill burners to high – that glass grill lid won’t shatter if a sudden thunderstorm interrupts your summer barbecue.

August 23, 2016


Kim Kennell
Home Tech
SCHOTT North America, Inc.