A Heady Examination of Foam in Its Many Forms

There’s something about foam that promises pleasure and fun: whether it’s the fizzy head on a glass of beer, the creamy froth of a cappuccino, the effervescence of champagne, the sudsy lather of a bubble bath or the flashing whiteness of a breaking wave. But there’s more to this bubbly substance than first meets the naked eye, ear, nose, tongue or skin.

In “Universal Foam,” Sidney Perkowitz, a scientist who holds a chair in physics at Emory University, offers a substantive account of this seemingly insubstantial substance. What, exactly, is foam? Well, as Perkowitz explains at the outset, “[f]oam is not exclusively a solid, liquid, or gas; it is made of bubbles or cells of gas within a liquid or a solid, and it combines characteristics of all three states of matter.” Liquid foams include everything from ocean spray to shaving cream. Solid foams, most of which start out as liquid foams, include pumice, Styrofoam, meringue and bread.

In seven chapters aimed at the intelligent layperson, Perkowitz offers an informative and illuminating survey of the subject. The first two chapters delve into the composition and structure of foam and the techniques that scientists have used to study it, from old-fashioned soap-and-water bubbles stretched over wire frames (not unlike a child’s toy) to complex three-dimensional models generated by computers.

The book’s subsequent five chapters, which make for livelier reading, deal with foam in all its multifarious forms. There are natural foams (both animate and inanimate) and man-made foams (both edible and inedible). The foam in our food, Perkowitz notes, seems to have no nutritional value in itself, but its presence enhances our enjoyment of eating and drinking: frothy milkshakes, delicate souffles, luscious mousses and fluffy rolls are just a few examples of the tempting forms foam can take. The bubbles in wine, beer and soda somehow seem to pique our taste buds and whet our appetites. Foam in food often indicates fresh preparation and culinary craft: A cappuccino can’t be canned, a hot souffle must be eaten soon after it’s made. Perkowitz describes the processes that go into producing some of these treats, from the ancient arts of brewing and bread-making to more recent inventions like the meringue (1720) and soda pop (the mid-19th century).

Less appetizing but even more useful are some of the other man-made foams, from the foamed plastic used for heat-proof coffee cups to aerogel, a gossamer-light substance sometimes called “frozen smoke” that is so strong, a pound or two can hold half a ton. Foams have been created to fight fires, insulate spacecraft, store rocket fuel and absorb the impact of explosions. Perkowitz provides intriguing accounts of the remarkable work done by scientists in this field.

Foam also appears in nature. From a planetary perspective, its most important form may be sea foam. “As far as we know,” writes Perkowitz, “our planet is the only place in the universe with open water that sustains foamy waves. . . .”

Perhaps this is why foam, like water, has such a powerful emotional aesthetic appeal: It is the matrix from which life itself is generated and sustained. The ancient Greeks pictured the goddess Aphrodite being born from the foam of the sea; modern scientists find clues to the origins of life in the bubbles on the ocean’s surface. The substance of life, Perkowitz explains, can be seen in terms of foam: “[A] single cell shares some characteristics of a bubble, and the collections of cells that form tissues and organs resemble an aggregation of bubbles.”

The porousness and resilience of solid foam can be seen in everything from sponges and cork to lungs and bones.

“Universal Foam” finally takes us beyond the familiar terrain of the kitchen, winery, laboratory and Earth itself to extraterrestrial realms. It is possible, notes Perkowitz, that the very structure of our universe resembles the structure of foam, with vast galaxies floating like film around even vaster bubbles of empty space. Universal indeed!