Engineer’s Art

Many families have a black sheep, someone who takes off on his or her own path rather than following family tradition. But few black sheep make as enduring-if a tad mundane-a contribution to society as Nathaniel Wyeth did with his invention of the plastic soda bottle.

Born into what many critics consider America’s foremost artistic family, Nathaniel Wyeth-named at birth Newell Convers Wyeth after his famous father-showed an early aptitude for engineering. In fact, his technical bent was so obvious almost from the start that at the age of three he was renamed after the senior N.C.’s brother Nathaniel, an engineer. While the rest of the Wyeth kids-younger brother Andrew and three sisters-went into art or music, Nathaniel studied engineering.

Wyeth spent most of his career at DuPont, working on various mechanical devices. One day in 1967, he wondered out loud why plastic wasn’t used for soda bottles. A colleague replied that plastic wasn’t strong enough; the carbonation would make the bottles expand and explode. Ever the tinkerer, Wyeth went out and bought a plastic bottle of detergent. He took it home, replaced the soap with ginger ale and left the bottle in the refrigerator. Sure enough, the container ballooned overnight and lodged itself tightly between the refrigerator shelves. So Wyeth began his quest to develop a plastic strong enough to keep carbonated beverages in check.

He knew that stretching nylon threads actually strengthens them, since it forces their molecules to align; to fortify plastic for bottles, however, he needed to line the molecules up in two dimensions rather than just one. His solution was a mold that resembled a test tube with screw threads-but the threads crisscrossed one another rather than running in a single spiral. When he pushed polypropylene through the mold, its molecules lined up in two dimensions, making the plastic strong enough to hold soda without deforming. But only after experimenting with thousands of polymers did Wyeth (above left) find one that gave him clear, light bottles and contained the carbonation without expanding.

In 1973, Wyeth filed for a patent on polyethylene terephthalate, or PET, soda bottles. Today billions of the bottles are produced each year in the United States, and they have become one of the most recycled household products. Polyester from recycled PET bottles goes into carpets, fabric, insulation and stuffing for furniture and sleeping bags.