Combs are one of our oldest tools, used by humans across cultures and ages for decoration, detangling, and delousing. They derive from the most fundamental human tool of all—the hand. And from the time that humans began using combs instead of their fingers, comb design has scarcely changed, prompting the satirical paper the Onion to publish a piece titled "Comb Technology: Why Is It So Far Behind the Razor and Toothbrush Fields?" The Stone Age craftsman who made the oldest known comb—a small four-toothed number carved from animal bone some eight thousand years ago—would have no trouble knowing what to do with the bright blue plastic version sitting on my bathroom counter.
For most of history, combs were made of almost any material humans had at hand, including bone, tortoiseshell, ivory, rubber, iron, tin, gold, silver, lead, reeds, wood, glass, porcelain, papier-mâché. But in the late nineteenth century, that panoply of possibilities began to fall away with the arrival of a totally new kind of material—celluloid, the first man-made plastic. Combs were among the first and most popular objects made of celluloid. And having crossed that material Rubicon, comb makers never went back. Ever since, combs generally have been made of one kind of plastic or another.
The story of the humble comb's makeover is part of the much larger story of how we ourselves have been transformed by plastics. Plastics freed us from the confines of the natural world, from the material constraints and limited supplies that had long bounded human activity. That new elasticity unfixed social boundaries as well. The arrival of these malleable and versatile materials gave producers the ability to create a treasure trove of new products while expanding opportunities for people of modest means to become consumers. Plastics held out the promise of a new material and cultural democracy. The comb, that most ancient of personal accessories, enabled anyone to keep that promise close.
What is plastic, this substance that has reached so deeply into our lives? The word comes from the Greek verb plassein, which means "to mold or shape." Plastics have that capacity to be shaped thanks to their structure, those long, flexing chains of atoms or small molecules bonded in a repeating pattern into one gloriously gigantic molecule. "Have you ever seen a polypropylene molecule?" a plastics enthusiast once asked me. "It's one of the most beautiful things you've ever seen. It's like looking at a cathedral that goes on and on for miles."
In the post–World War II world, where lab-synthesized plastics have virtually defined a way of life, we've come to think of plastics as unnatural, yet nature has been knitting polymers since the beginning of life. Every living organism contains these molecular daisy chains. The cellulose that makes up the cell walls in plants is a polymer. So are the proteins that make up our muscles and our skin and the long spiraling ladders that hold our genetic destiny, DNA. Whether a polymer is natural or synthetic, chances are its backbone is composed of carbon, a strong, stable, glad-handing atom that is ideally suited to forming molecular bonds. Other elements—typically oxygen, nitrogen, and hydrogen—frequently join that carbon spine, and the choice and arrangement of those atoms produces specific varieties of polymers. Bring chlorine into that molecular conga line, and you can get polyvinyl chloride, otherwise known as vinyl; tag on fluorine, and you can wind up with that slick nonstick material Teflon.
Plant cellulose was the raw material for the earliest plastics, and with peak oil looming, it is being looked at again as a base for a new generation of "green" plastics. But most of today's plastics are made of hydrocarbon molecules—packets of carbon and hydrogen—derived from the refining of oil and natural gas. Consider ethylene, a gas released in the processing of both substances. It's a sociable molecule consisting of four hydrogen atoms and two carbon atoms linked in the chemical equivalent of a double handshake. With a little chemical nudging those carbon atoms release one bond, allowing each to reach out and grab the carbon in another ethylene molecule. Repeat the process thousands of times and voilà!, you've got a new giant molecule, polyethylene, one of the most common and versatile plastics. Depending on how it's processed, the plastic can be used to wrap a sandwich or tether an astronaut during a walk in deep space.