Finding and formulating the fizz factor

Science that applies to the laboratory - or the taproom.

Posted: April 30, 2007

When David Srolovitz and Robert MacPherson went to a Princeton pub last week, they weren't just two Jersey guys going out for a beer. They saw the creamy foam through the cold eye of science.

The two had just published a paper in the British journal Nature about the behavior of foam, ceramics and other "three-dimensional microstructures" - offering a solution to a problem that has stymied materials scientists for 50 years.

It is well known that such networks of bubbles, grains or cells tend to become "coarser" over time: some cells become larger, while others shrink and eventually disappear.

More than 50 years ago, scientists figured out how fast cells grow or shrink - but only in two dimensions. Srolovitz and MacPherson now have a formula for 3-D, though it is beyond the realm of the average beer-drinker. It's based on the sum of the length of the sides of a given cell and also on its "mean width" - a linear representation of the volume.

In an accompanying review of the topic, Carnegie Mellon's David Kinderlehrer wrote: "The result is not merely novel, but also intellectually exciting."

Srolovitz, a Willingboro native and physics professor at New York's Yeshiva University, said the formula could help to refine the manufacturing of ceramics and metals, to get just the right strength and toughness. In beer, he's not so sure how it would help, but said smaller bubbles generally mean a creamier foam.

MacPherson, a world-renowned geometry specialist, is a professor at the Institute for Advanced Studies in Princeton.

While the final proof took them a few months, the duo whipped up a basic solution to the foam problem in just a few hours. We'll drink to that.

- Tom Avril

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