Written on 05/16/2019

Heather Warmke and St. Thomas More student Austin Lega check out the effect of liquid nitrogen on a balloon.

Your choice: Learn science by staring at a periodic table or by eating some ice cream.

Of course, every youngster this side of Enrico Fermi would go for the latter. And Heather Warmke is happy to provide the opportunity.


Alice Mayfield gets ready for a demonstration of the effects of liquid nitrogen on a flower.

She and her husband, Jeff, own the Upper St. Clair location of Sub Zero Nitrogen Ice Cream, using a patented process to make America’s favorite frozen treat. The founders of the business, Jerry and Naomi Hancock of Utah, encourage franchisees to conduct educational programs about liquid nitrogen and its effects on various everyday items.


So Heather and friend Alice Mayfield, both Upper St. Clair residents who have almost three decades’ worth of combined experience as teachers, are making the rounds to fill youngsters in on the wonders of Element No. 7.

“How cold is liquid nitrogen?” Warmke asked students during a recent visit to St. Thomas More School in Bethel Park.

One answer: “Very.”

That’s true, but: “I need a number.”

It turns out that nitrogen’s boiling point is minus 320.4 degrees Fahrenheit, meaning it becomes gas at an extremely low temperature. And that’s quite OK, Warmke likes to explain, because 78 percent of the earth’s atmosphere is nitrogen.

Heather Warmke fills a bowl with liquid nitrogen for a demonstration.

“They learn something that almost every adult does not know, that there’s more nitrogen in the air than oxygen,” she said, and it’s not even close: just 21 percent is the stuff we need to breathe in to live. “When I teach kids that, they’re so excited to go home and tell their parents.”

Warmke and Mayfield regularly perform a series of demonstrations to show liquid nitrogen’s role in changing states of matter, with the use of a balloon as one example. Blowing into the balloon fills it with exhaled carbon dioxide, and sticking it into a bowl of liquid nitrogen has this effect: “What’s happening is the liquid nitrogen is so cold that the carbon dioxide inside the balloon is shrinking,” Warmke told the St. Thomas More students. “The molecules are shrinking so much that it got flat.”

In another demonstration, the contents of a water bottle received the liquid-nitrogen treatment.

Heather Warmke assists St. Thomas More School student Reed Farmerie in determining the effect of liquid nitrogen on a flower.

“It is boiling,” Warmke revealed. “Nitrogen is a gas that needs to be released, meaning if I put a lid on this, what would happen to my water bottle?”

Most of the boys ventured a particular answer, which she promptly verified. “That’s right. It would explode. But I’m not going to do that, as fun as it may seem.”

The science lesson, of course, wrapped up with Warmke and Mayfield making Sub Zero’s featured product and the youngsters devouring it.

“I could go in there and just make the ice cream, but it’s not nearly as exciting,” Warmke said. “They need to learn the process as to how it gets like that.”

Regarding Sub Zero, she learned about the business while vacationing with her husband and two children, Madison and Luke, in Sarasota, Fla.

Heather Warmke subjects a balloon to a bowl of liquid nitrogen

“There were 40 people in line out the door,” she recalled, but the wait turned out to be worthwhile. “It was truly the best ice cream I’d ever tasted.”

And the reason: “The molecules have not had a chance to separate,” Warmke explained. “If you’ve ever had anything gritty or freezer-burned, the molecules have separated. The water has gotten in and frozen, causing it to be an ice crystal.”

In Alice Mayfield’s hand is a semi-solid gummy bear that will turn solid when exposed to liquid nitrogen, and then go back to its original state in someone’s mouth.

At the Warmkes’ store in Siena at St. Clair is a 7,000-pound tank of nitrogen, from which they fill smaller tanks to take on the road. Along with educational purposes, that also includes ice cream sales at various events.

“We’re very much involved in the community, and we give back,” Warmke said, with 20 percent of the proceeds always donated to hosting organizations. And no truck is necessary.

“I just do two tables and my tanks. We don’t even require electricity.”

For more information about Sub Zero’s educational programs, contact jhwarmke.subzero@gmail.com.