After ten or fifteen minutes of driving I left the cab and wandered about. I had come to a slope ridged by low terraces, each bearing a line of rubber trees. Beyond the crest of the slope was a sharp drop-off, and beyond that were hills, irregular as the wrinkles of a sheet thrown to the floor, their colors fading with distance in the hazy afternoon. Every living thing that I could discern was a rubber tree.
The driver was walking with me. He said he had not been to this area since he was young. The hills had been full of mammals and birds then. All had been replaced by rubber. Even the insects were still. It may have been the quietest forest I had ever walked in. Every now and then there was a quick breath of wind and the leaves rippled like tiny flags, momentarily exposing their satin tops. “There’s nothing left,” the driver said, visibly upset. “People want to cut and cut and plant and plant—damn them.”
More than a century ago, a handful of rubber trees had come to Asia from their home in Brazil. Now the descendants of these trees carpeted sections of the Philippines, Indonesia, Malaysia, Thailand, and this part of China. Across the border H. brasiliensis was marching into Laos and Vietnam. A plant that before 1492 had never existed outside of the Amazon basin now dominated Southeast Asian ecosystems. Indeed, rubber reigned over such a wide area that botanists had long warned that a single potato blight–style epidemic could precipitate an ecological calamity—and, just possibly, a global economic breakdown.
Guide strips for latex and collection cups mark this rubber plantation in Xishuangbanna, China, an autonomous southern area near the Laotian border. (Photo credit 7.7)
In Longyin Le I wandered from house to house, talking to farmers about rubber. To a person they were thankful for the opportunities it provided. Rubber was putting food on the table, paying for children’s education, building and repairing roads. Just as the potato played a critical part in helping Europe escape the Malthusian trap (though perhaps only for a time), rubber had helped bring about the Industrial Revolution, the transition from an economy based on manual labor and draft animals to one based on mechanized manufacturing. The people in Longyin Le were its latest beneficiaries. As I looked over the lush miles of birdless trees I could still hear their grateful voices. And rising like vapor were other voices, the countless men and women whose lives, for better and worse, had become entwined with this plant: hapless slaves, visionary engineers, hungry merchants, obsessed scientists, imperial politicians. This landscape of alien trees was the creation of countless different hands in many places, and it was much older than forty-five.
“GREASE CHEMISTRY”
In May of 1526 Andrea Navagero, the Venetian ambassador to Spain, attended an entertainment in Seville staged for the royal court. Seven years earlier, Hernán Cortés, acting without the authorization of the Spanish throne, had invaded Mexico and toppled the Triple Alliance (Aztec empire). The king and queen had to decide what to do with their millions of new subjects. Some argued that they should be enslaved, because they were naturally inferior; others, that they should be converted to Christianity and made full citizens of Spain. To demonstrate the intelligence, skills, and noble demeanor of the peoples of the Triple Alliance, the antislavery faction of the Spanish church had imported a group of them to Seville. The Indians divided into teams and played a showcase version of the Mesoamerican sport of ullamaliztli, which the Venetian ambassador attended.
Navagero was an insatiably curious man who translated poetic and scientific classics, wrote a history of Venice, and performed biological experiments—he created a private botanical garden in 1522, among the first on the continent. He was mesmerized by ullamaliztli, which he seems to have thought was a performance akin to a juggling act (team sports had been played in the Roman empire but were then almost unknown in Europe). In ullamaliztli two squads vied to drive a ball through hoops on the opposite ends of a field—an early version of soccer, one might say, except that the ball was never supposed to touch the ground and players could hit it only with their hips, chests, and thighs. Dressed in padded breechcloths and wrist protectors like thick fingerless mittens, the players knocked a fist-sized ball back and forth “with so much dexterity that it was marvelous to see,” Navagero reported, “sometimes throwing themselves completely on the ground to return the ball, and all of this done with great speed.”
As fascinating to Navagero as the ball game was the ball itself. European balls were typically made of leather and stuffed with wool or feathers. These were something different. They “bounded copiously,” Navagero said, ricocheting in a headlong way unlike anything he had seen before. The Indian balls, he guessed, were somehow made “from the pith of a wood that was very light.” Equally puzzled was Navagero’s friend Pietro Martire d’Anghiera, who saw a game at about the same time. When the Indian balls “touch the ground, even though lightly thrown, they spring into the air with the most incredible leaps,” d’Anghiera wrote. “I do not understand how these heavy balls are so elastic.”
The royal chronicler Gonzalo Fernández de Oviedo y Valdés fared little better. In his General and Natural History of the Indies (1535), the first official account of Spain’s foray into the Americas, he tried to describe bouncing, a term not then in the Spanish language: “These balls jump much more than our hollow balls—by far—because even if they are only let slip from the hand to the ground, they rise much further than they started, and they make a jump, and then another and another, and many more, decreasing in height by itself, like hollow balls but more so.” Indians made the strange, springy material of the balls, he wrote, by combining “tree roots and herbs and juices and a combination of things.… [A]fter [the mixture] is dried, it becomes rather spongy, not because it has holes or voids like a sponge, but because it becomes lighter, as if it were flabby and rather heavy.” Wait a minute, one wants to say: how could something “become lighter” yet be “rather heavy”?
Europeans like German artist Christoph Weiditz were fascinated by the native ballplayers who toured Spain in the 1520s—and by the rubber ball, which was unlike anything ever seen in Europe. (Photo credit 7.1)
Navagero, d’Anghiera, and Oviedo had a right to be confounded: they were encountering a novel form of matter. The balls were made of rubber. In chemical terms, rubber is an elastomer, so named because many elastomers can stretch and bounce. No Europeans had ever seen one before.
To engineers, elastomers are hugely useful. They have tucked rubber and rubber-like substances into every nook and crack of the home and workplace: tapes, insulation, raingear, adhesives, footwear, engine belts and O-rings, medical gloves and hoses, balloons and life preservers, tires on bicycles, automobiles, trucks, and airplanes, and thousands of other products. This didn’t happen immediately: careful studies of rubber didn’t occur until the 1740s. The first simple laboratory experiments, in 1805, gave little hint that rubber might be useful—although the scientist, John Gough, did discover the fact, key to later understanding, that rubber heats up when stretched.1 Only in the 1820s did rubber take off, with the invention of rubber galoshes.
Take off for Europeans and Americans, that is; South American Indians had been using rubber for centuries. They milked rubber trees by slashing thin, V-shaped cuts on the trunk; latex dripped from the point of the V into a cup, usually a hollowed-out gourd, mounted on the bark. In a process reminiscent of making taffy, Indians extracted rubber from the latex by slowly boiling and stretching it over an intensely smoky fire of palm nuts. When the rubber was ready, they worked it into stiff pipes, dishes, and other implements. Susanna Hecht, a UCLA geographer who has worked extensively in Amazonia, believes that native people also waterproofed their hats and cloaks by impregnating the cloth with rubber. European colonists in Amazonia were manufacturing rubberized garments by the late eighteenth century, including boots made by dipping foot-shaped molds into bubbling pots of latex. A few pairs of boots made their way to the United States. Cities like Boston, Philadelphia, and Washington, D.C., were built on swamps; their streets were thick with mud
and had no sidewalks. Rubber boots there were a big hit.
The epicenter of what became known as “rubber fever” was Salem, Massachusetts, north of Boston. In 1825 a young Salem entrepreneur imported five hundred pairs of rubber shoes from Brazil. Ten years later, the number of imported shoes had grown to more than 400,000, about one for every forty Americans. Villagers in tiny hamlets at the mouth of the Amazon molded thousands of shoes to the dictates of Boston merchants. Garments impregnated with rubber were modern, high-tech, exciting—a perfect urban accessory. People flocked to stores.
The crash was inevitable. The idea of impermeable rubber boots and clothes was more exciting than the fact. Rubber simply didn’t work very well. In cold weather, the shoes became brittle; in hot weather, they melted. Boots placed in closets at the end of winter turned into black puddles by fall. The results smelled so bad that people found themselves burying their footgear in the garden. Daniel Webster, the senator and secretary of state, liked to tell the story of how he received a rubber cloak and hat as a gift. He wore them on a cold evening. By the time he reached his destination the cloak had become so rigid that he stood it in the street by the front door. Supposedly he propped the hat on top. “Some decorous gentlemen among us can also remember,” one critic wrote later, “that, in the nocturnal combats of their college days, a flinty India-rubber shoe, in cold weather, was a missive weapon of highly effective character.” Returned goods inundated rubber dealers. Public opinion swung violently against rubber.
Just before the collapse, in 1833, a bankrupt businessman named Charles Goodyear became interested in—and obsessed by—rubber. It was typical of Goodyear’s entrepreneurial acumen that he began to seek financial backing for a rubber venture just at the time investors were planning their exits from the field. A few weeks after Goodyear announced his intent to produce temperature-stable rubber he was thrown into debtor’s prison. In his cell he began work, mashing bits of rubber with a rolling pin. He was untroubled by any knowledge of chemistry but boundlessly determined. For years Goodyear wandered about the northeastern United States in a cloud of penury, trailed by his hungry wife and children, dodging bailiffs and pawning heirlooms. All the while he was mixing toxic chemicals, more or less randomly, in the hope that they would make rubber more stable. The Goodyears lived in an abandoned rubber factory in Staten Island. They lived in an abandoned rubber factory in Massachusetts. They lived in a shack in a Connecticut neighborhood called Sodom Hill (the name indicated its wholesomeness). They lived in a second abandoned rubber factory in Massachusetts. Sometimes the houses had no heat or food. Two of Goodyear’s children died.
Taking his cue from a dream told to him by another rubber obsessive, Goodyear began mixing rubber with sulfur. Nothing happened, he said later, until he accidentally dropped a lump of sulfur-treated rubber onto a wood stove. To his amazement, the rubber didn’t melt. The surface charred, but the inner material changed into a new kind of rubber that retained its shape and elasticity at high temperatures. Goodyear threw himself into reproducing the accident, a task impeded by his inability to afford any laboratory apparatus—he had to traipse from neighbor to neighbor, asking to use their wood stoves. Sometimes the sulfur process worked, sometimes it didn’t. Goodyear kept working, frustrated, hungry, haunted. When he was again thrown into debtor’s prison, he wrote to acquaintances from his cell, asking for supplies “to establish an India rubber factory for myself on the spot.” Eventually he borrowed money and paid the debt. A month later he was in another jail.
Along the way he befriended a young Englishman. Goodyear gave him a few of his successful samples and asked him to seek investors in Britain. By a circuitous path two thin, inch-and-a-half-long strips of Goodyear’s processed rubber ended up in the fall of 1842 at the laboratory of Thomas Hancock, a Manchester engineer who had developed processes for manipulating rubber. Hancock had no idea where these bits of rubber had originated. But he quickly realized that they didn’t melt in hot weather or become stiff in cold weather. The question was whether he could duplicate the accomplishment. It is unclear how much he was able to learn from Goodyear’s samples. Later he claimed to have “made no analysis of these little bits” from the other man—a remarkable demonstration of incuriosity, if true. In any case Hancock was more organized and knowledgeable than Goodyear and had better equipment. For a year and a half he systematically performed hundreds of small experiments. Eventually he, too, learned that immersing rubber in melted sulfur would transform it into something that would stay stretchy in cold weather and solid in hot weather. Later he called the process “vulcanization,” after the Roman god of fire. The British government granted Hancock a patent on May 21, 1844.
Identifying the inventor of the process of vulcanization, which makes rubber usable for industrial purposes, is complex. Charles Goodyear (left) had the basic idea first, but never fully understood the process; Thomas Hancock (right) patented the process before Goodyear and understood it better, but likely derived inspiration from seeing Goodyear’s initial samples. (Photo credit 7.2)
Three weeks later, the U.S. government awarded Goodyear his vulcanization patent. A glance at the patent shows that Goodyear never fully understood the process: a key ingredient, he claimed, was white lead, a metal-based pigment whose effect on rubber’s stability is “secondary, if anything,” according to E. Bryan Coughlin, of the Silvio O. Conte National Center for Polymer Research at the University of Massachusetts. “I’m not sure, because it’s not a standard treatment—maybe it has some catalytic effect.” By contrast, Coughlin told me, Hancock’s patent was “pretty straightforward.” Hancock stirred softened rubber into sulfur heated to 240°–250° F, just above its melting point. The longer he subjected it to heat, the more elasticity it lost. “That’s pretty much what I teach my students,” Coughlin said.
Goodyear didn’t understand the recipe for vulcanization, but he did understand that at last he had a business opportunity. Showing a previously unsuspected knack for publicity stunts, he spent $30,000 he did not have to create an entire room made of rubber for the Great Exhibition of 1851 at the Crystal Palace in London, the first world’s fair. Four years later he borrowed $50,000 more to display an even more lavish rubber room at the second world’s fair, the Exposition Universelle in Paris. Parisians lost their urban hauteur and gawped like rubes at Goodyear’s rubber vanity table, complete with rubber-framed mirror; arranged on the top was a battalion of rubber combs and rubber-handled brushes. In the center of the rubber floor was a hard rubber desk with a rubber inkwell and rubber pens. Rubber umbrellas stood at attention in a rubber umbrella-stand in the corner of two rubber walls, each decorated with paintings on rubber canvases. For weapons fans, there was a stand of knives in rubber sheaths, swords in rubber scabbards, and rifles with rubber stocks. Except for the unpleasant rubber smell, Goodyear’s exhibit was a triumph. “Napoleon III invested him with the Legion of Honor,” wrote the diplomat and historian Austin Coates, “and a Paris court sent him to prison for debt.” He received the medal in his cell. Goodyear was forced to sell some of his wife’s possessions to pay for their trip home. He died four years later, still awash in debt.
Afterward, Americans lionized Goodyear as a visionary. Books extolled him to children as an exemplar of the can-do spirit; a major tire company named itself after him. Meanwhile, Coates noted, “Hancock received English treatment: due respect while living, fading notice when dead, and on some suitable centenary thereafter, a postage stamp.”
Neither Goodyear nor Hancock had any idea why sulfur stabilized rubber—or why, for that matter, unadulterated rubber bounced and stretched. Nineteenth-century scientists found bouncing balls exactly as mystifying as sixteenth-century Spaniards. Stretch a thin hoop of iron: it will elongate slightly, then snap in two. A rubber band, by contrast, can stretch to three times its ordinary length, then return to its original shape. Why? And why did sulfur stop rubber from melting in the summer? “Nobody knew,” Coughlin told me. “It was a huge puzzle. And it
was made harder by the fact that a lot of chemists didn’t really want to study it.”
The last half of the nineteenth century was a heady time for chemistry. Researchers were deciphering the underlying order of the physical world. They were placing the chemical elements into the periodic table, discovering the rules by which atoms combine into molecules, and learning that molecules could form regular crystals with structures that could be precisely identified.
Nowhere in these tidy intellectual schemes was a place for rubber. Chemists couldn’t make it form crystals. Worse, many standard chemical tests on rubber produced nonsensical answers. The analyses demonstrated that each rubber molecule was made up of carbon and hydrogen atoms. No problem there. But they also indicated that the carbon and hydrogen were piled up into jumbo-sized molecules made up of tens of thousands of atoms. To most chemists, this was absurd—molecules are the fundamental building blocks of chemical compounds, and no fundamental building block should be that big.
The obvious conclusion, chemists said, is that rubber must be a colloid: one or more compounds finely ground up and dispersed throughout other compounds. Glue is a colloid; so are peanut butter, bacon fat, and mud. Because colloids aren’t one substance but a mishmash of many different substances, they have no fundamental constituents. Looking for one would be like trying to find the molecular building blocks of a garbage heap. The chemistry of rubber was, one German researcher scoffed, Schmierenchemie. Literally, Schmierenchemie means “grease chemistry,” though Coughlin told me it might be better translated as “the chemistry of the gunk on the bottom of a test tube.”