Technical thinking: We still don’t know everything about ice

I recently saw my first icicle of the year. It was a small, wiggly thing. I know why thanks to some of the ice-related discoveries of the past year.

Written by Mark Jones

In an example of curiosity driven research, the observation that icicles aren’t perfect cones led researchers to ask why. No one had explained why previously. Research showed impurities make ripples. It should follow that pure water would make perfect, smooth cones. It doesn’t. Mysteries remain. After centuries of living with icicles, there are still things we are just beginning to understand. More curiosity driven research is required.

Reports of practical use of ice came out in 2023. Ice was touted as a sustainable, earth abundant building material. Multiple reports. All bring back memories of pykrete, the composite with ice as the continuous phase. If it sounds like something out of MythBusters, it is. Material properties were confirmed. Adding sawdust to water and freezing it yields a material actually floated to be used in making an aircraft carrier in World War II. Today’s research harkens to pykrete, with new additions to the composite mix. Inorganic microparticles, polypropylene and basalt, and organic and inorganic nanoparticles are just some of the materials used to improve the mechanical properties. Ice is an ephemeral building material, one limited to climates where the refrigeration is natural. Even in naturally cold climates, warm weather threatens. Reconstruction is inevitable certainly dampening any sustainability claims. It is a practical use of a local, inexhaustible, albeit seasonal, resource.

Other practical ice uses were reported, not for building but for human consumption. Starbucks announced it was changing the ice the company used. All ice for consumption begins its life as water injected into a cold vessel. Ice trays give us frozen chucks used without further processing: hard crystalline chunks. Nugget ice is different. A big frozen block is whittled into little chunks that are compressed to make ice nuggets or pebbles. The loosely aggregated collections aren’t hard. Breaking a tooth is nearly impossible. So is choking. Long popular with hospitals, nugget ice is spreading to Starbucks. Nugget ice is more satisfying to chew, at least according to most surveys, and offers some other advantages. The machines are more sustainable, using 40% less water and 15% less energy. Less water loss due to purging and more on-demand production underly the sustainability advantages.

Starbucks may be moving on from big ice, but others embrace it. Camper English released The Ice Book, becoming the de factoice expert of 2023. Much of the reporting centered on his work to make clear ice. The aesthetics of clear ice make it preferable, especially in high-end cocktails. Camper is certainly to be commended. He methodically experimented to find a way to make the big, clear ice he wanted. What he found was directional cooling. In order to get clear ice, you want the ice to grow from a single edge.

Camper did something I’ve done many times. He rediscovered something that was actually well-known. The adage I heard early in my career was “two weeks in the lab can save fifteen minutes in the library.” Clear ice wasn’t well described in either academic or popular press before Camper. It was, however, well described in the patent literature. Going back to at least 1973, directional cooling was known to make clear ice.

There are several things to take away from the current fascination with ice. I’ll feel a little better munching on nugget ice, knowing it is slightly better for the planet. I’ll appreciate wiggly icicles more. I’ll also remember to check patent literature when seeking practical, technical solutions.