Vulcanized Rubber (1839): Charles Goodyear's Accidental Discovery

Vulcanized rubber is natural rubber that has been heated with sulphur to make it strong, elastic and stable in heat and cold. The American inventor Charles Goodyear discovered the effect in early 1839 in Woburn, Massachusetts, and patented the process in 1844. Vulcanization turned rubber from a curiosity that melted in summer into one of the essential materials of the industrial world.

Background: the rubber problem

Natural rubber, made from the milky latex of trees such as the South American Hevea brasiliensis, had long been used by peoples of the Americas for balls, containers and waterproofing. In Europe it was at first a novelty, named “rubber” in English because it could rub out pencil marks. In the 1820s Charles Macintosh in Scotland used it to make waterproof cloth, and a “rubber fever” swept the United States in the early 1830s as companies made shoes, coats and wagon covers.

The boom soon collapsed. Untreated rubber turned soft, sticky and foul-smelling in summer heat and stiff and brittle in winter cold. Many companies failed, and customers returned piles of melted goods.

Goodyear’s search

Charles Goodyear (1800–1860), born in New Haven, Connecticut, had failed in the hardware business and spent time in debtors’ prison. In 1834 he visited the Roxbury India Rubber Company’s shop in New York and became convinced that he could make rubber stable. For years he mixed rubber with almost anything he could find, including magnesia, lime and nitric acid, while his family lived in poverty.

In 1838 he met Nathaniel Hayward, a former employee of a rubber factory in Woburn, who had found that adding sulphur and drying the rubber in the sun reduced its stickiness. Goodyear bought the rights to Hayward’s method and kept experimenting.

The discovery of 1839

In early 1839, according to Goodyear’s own later account, a sample of rubber mixed with sulphur came into contact with a hot stove. Instead of melting, it charred at the edges like leather, while the rim remained elastic. Goodyear realised that heat, the very thing that ruined ordinary rubber, could transform it when sulphur was present.

The observation was only a beginning. It took Goodyear about five more years of trial and error, often on borrowed money, to work out reliable temperatures, timings and mixtures. He received US patent number 3,633 on 15 June 1844. Goodyear himself insisted that the discovery was not pure luck, writing that it came to someone who had been searching for it.

The race with Thomas Hancock

In England the rubber manufacturer Thomas Hancock, a partner of Charles Macintosh, examined samples of Goodyear’s rubber that had been brought to Britain in the early 1840s. Working out that sulphur was involved, he developed his own process and patented it in Britain on 21 November 1843, shortly before Goodyear applied for a British patent. Goodyear later challenged Hancock in court but lost, so he never controlled the process in Britain. The word “vulcanization” was coined in Hancock’s circle by his friend William Brockedon.

In the United States Goodyear licensed his patent to manufacturers but faced widespread infringement. In 1852, in the case of Goodyear v. Day, his patent was upheld after he was represented by the famous lawyer and statesman Daniel Webster.

Later life and legacy

Goodyear exhibited a whole pavilion of rubber goods at the Great Exhibition in London in 1851 and again at the Paris Exposition of 1855, where he was awarded a medal and the Legion of Honour, though he was also briefly imprisoned for debt in Paris. Poor at business and always spending on new experiments, he died in New York on 1 July 1860, owing large sums.

His discovery created vast industries. Vulcanized rubber was used for footwear, waterproof clothing, hoses, belts and seals for steam engines, and insulation for telegraph cables. Hard rubber, or ebonite, made by heating rubber with more sulphur, was patented by his brother Nelson Goodyear in 1851. The arrival of the pneumatic tyre in 1888 and then the motor car turned rubber into a strategic material.

The demand had a darker side. The rush to collect wild rubber in the late 19th and early 20th centuries led to brutal forced labour in the Amazon and in the Congo Free State, where millions are estimated to have died from violence, famine and disease under King Leopold II’s regime.

Timeline

• 1820s: Charles Macintosh patents waterproof rubberised cloth in Scotland.
• 1834: Goodyear begins experimenting with rubber.
• 1838: Goodyear acquires Nathaniel Hayward’s sulphur method.
• 1839, early: Goodyear observes the effect of heat on rubber mixed with sulphur.
• 1843, 21 November: Thomas Hancock patents vulcanization in Britain.
• 1844, 15 June: Goodyear receives US patent 3,633.
• 1852: Goodyear wins the case of Goodyear v. Day.
• 1860, 1 July: Goodyear dies in New York.

Why it matters

Vulcanization turned a temperamental natural product into a dependable engineering material. Tyres, seals, hoses, insulation and countless everyday goods depend on it, and the process Goodyear found in 1839 remains, in refined form, the basis of the rubber industry today.