It's a summer chemistry tradition. Once a week, all work stops for ice cream.
This isn't store-bought ice cream. It's not home-made ice cream, either. For years, every summer Wednesday at 3 p.m., students and faculty in the chemistry department have gathered together for lab-made ice cream.
The ice cream mix is just like the stuff you'd whip up in the kitchen, but this ice cream is frozen in a matter of seconds with liquid nitrogen.
The tradition began years ago when a research group headed by Department Chair Gary Rice came up with the idea. He and his students discussed possibilities, looked online for recipes and gave birth to a tradition.
"More and more people got involved," Rice said. "So the next year each lab took a week. Every year it gets better and better." The early days were guided by an experimental ethos that didn't always turn out good ice cream. Rice recalled a rutabaga sorbet and some disappointing efforts involving Captain Crunch. His favorite flavor over the years? Chocolate mint, made with crumbled mint Oreos.
When Professor Lisa Landino's lab has ice cream duty the scene resembles the opening of Shakespeare's Macbeth--three female students take the place of witches and big bowls of milky liquid stand in for cauldrons. One student crumbles pieces of shortcake into a mix already laced with bobbing strawberries. The other flavors of the week are cinnamon and chocolate-peanut butter.
Landino arrives and takes a student down the hall to fill a dewar with liquid nitrogen. (Dewars are essentially lab-grade thermos bottles that come in all sizes.) The two chemists share a pair of insulated gauntlets, because the liquid nitrogen whistling into the dewar is well below -300 degrees Fahrenheit.
One extra benefit of lab-made ice cream: younger students become comfortable handling cryogenic materials. Liquid nitrogen is an everyday staple in labs, with a vast range of non-dairy applications. Nitrogen in itself is not scary stuff--but in liquid form it can give you frostbite pretty quickly.
Back in the lab the dewar is uncorked and liquid nitrogen is poured directly into the strawberry shortcake mix. The nitrogen immediately begins to boil, absorbing heat from the ice cream mix, which solidifies as it freezes. This is time for collaborative lab technique: one person pours, slowly; a second stirs, rapidly. Thick, cold vapor spills over the bowl's rim and rolls across the table. The MacBeth resemblance is renewed.
Each summer around 50 students, graduate and undergrad, are working in chemistry. Add faculty, staff and visitors and three big bowls of ice cream can disappear almost as quickly as boiling nitrogen vapor.
"We're all part of one big chemistry family," Landino says to the swelling group of faculty and students who watch her nudge errant bits back into the smoking bowl. "So it doesn't matter if I get my fingers in it."
The eating and socializing is over almost as quickly as the ice cream is made. Everyone goes back to their labs, a few licking their spoons. These are busy chemists, so there's no time to wait for ice cream to harden, or to linger over a cup of delicious lab-made strawberry shortcake.