From seaweed, a lighter-than-air solid.

Floating on soap bubbles overflowing from a jar, this airy, white solid represents the latest in featherweight materials. But made in its densest form, SEAgel (Safe Emulsion Agar gel) can support thousands of times its own weight. And it's even edible.

Produced from a natural material - seaweed - with a simpler technology than the light-as-air aerogels (SN: 5/5/90, p.287), SEAgel is 10 percent lighter than either air or aerogels. Only the air trapped in its microscopic pores keeps it on the ground, says Robert L. Morrison, a physical chemist who helped develop SEAgel at the Lawrence Livermore (Calif.) National Laboratory.

Morrison starts with agarose, a commercially available product extracted from help for use as a thickener in foods. He dissolves and emulsifies the agarose, then cools the emulsion to make a gel. He freezes and then freeze-dries the gel to make SEAgel's final gossamer form. He varies the density by varying the initial amount of agarose in his solution.

"The strength increases as the density goes up," Morrison says. Because this solid foam insulates well, he thinks it could replace balsa wood a sound barrier in aircraft or high-speed rail cars. It may also prove useful as an inexpensive insulation for refrigerators or oil tankers.

Agarose's low cost and SEAgel's simple processing make this an attractive new material, Morrison says. And because SEAgel is biodegradable, it could prove a better packing material than plastic chips, he says. Others have suggested using the product as a time-release packaging for medication, insecticide or even fertilizer.