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Before the 1840s, a rubber raincoat was a gamble. In summer it went soft and sticky; in winter it turned stiff and cracked. Charles Goodyear, an American hardware merchant with no chemistry training, spent years trying to fix this, and his answer, heating rubber with sulphur, is still the basis of tyres, hoses and shoe soles. This post covers what he found, reads his patent, and works through the numbers in his recipe.
Who was Charles Goodyear?
Britannica's biography gives his dates as 29 December 1800, New Haven, Connecticut, to 1 July 1860, New York City. He began as a partner in his father's hardware business, which went bankrupt in 1830. He then set out to find a way to treat india rubber so that it would lose its stickiness and stand up to heat and cold.
His first method, a nitric acid treatment, failed: in 1837 he contracted to make mailbags for the US government, but the rubber fabric proved useless in hot weather. He then worked with Nathaniel Hayward, who had found that rubber treated with sulphur was less sticky, and bought Hayward's process. Britannica records that in 1839 Goodyear accidentally dropped some rubber mixed with sulphur on a hot stove, and so discovered vulcanisation.
What does the 1844 patent say?
Goodyear's US Patent No. 3,633, dated 15 June 1844, states his "principal improvement" as combining sulphur and white lead with india rubber and heating the compound "at a regulated temperature". After this, he wrote, the material would not soften in sunlight or at any temperature below the one used to make it, would not be harmed by cold, and would resist oils and turpentine, which normally dissolve rubber.
He gives a preferred recipe: 25 parts india rubber, 5 parts sulphur and 7 parts white lead. The heating temperature could vary from 212 to 350 degrees Fahrenheit, with about 270 degrees working well.
Worked example: reading the recipe like a chemist
Total parts: 25 + 5 + 7 = 37.
Sulphur as a share of the mixture: 5 ÷ 37 ≈ 0.135, or about 13.5%.
Sulphur relative to rubber: 5 ÷ 25 = 0.20, so 20 parts sulphur per 100 parts rubber.
Temperatures in Celsius: use C = (F − 32) × 5/9.
212 °F → (212 − 32) × 5/9 = 100 °C, the boiling point of water.
270 °F → 238 × 5/9 ≈ 132 °C.
350 °F → 318 × 5/9 ≈ 177 °C.
So the window ran from the temperature of boiling water to well above it, which is why a hot stove did the job by accident and a kitchen kettle would not.
A common mistake in step 2 is to divide 5 by 25 and call it the share of the mixture. That gives sulphur per unit of rubber, not per unit of the whole batch. Always say what your percentage is "of".
Why did vulcanisation not make Goodyear rich?
Britannica describes a hard road. He received his first patent in 1844 but had to fight many infringements in court, winning the decisive case only in 1852. In England and France he lost his patent rights, a French company using his process failed, and in December 1855 he was imprisoned for debt in Paris. When he died, he left debts of about $200,000, even though his invention had made fortunes for others. He wrote an account of his work, Gum-Elastic and Its Varieties, published in two volumes in 1853 to 1855.
Why does it matter for chemistry students?
Vulcanisation is one of the earliest cases of people changing a polymer's properties by changing how its chains are connected, long before chemists agreed that rubber was made of long molecules. That idea came later, a story told in our post on Hermann Staudinger and polymers. For a fully synthetic polymer designed from scratch, read about Wallace Carothers and nylon.
What can a student take from Goodyear's way of working?
Failure is data. The ruined mailbags told him that his first treatment did not survive heat, which is the property he had to fix.
Be ready for the accident. The stove incident only mattered because he had spent years on the problem and recognised what he saw.
Write down the recipe. His patent gives exact proportions and a temperature range, which is why we can still check it today.
If the idea of chains and cross-links is new to you, the Fermi Concept Library covers every concept in physics, chemistry, biology, mathematics and computing, so you can read up on polymers one idea at a time.
Next step: convert the recipe to grams for a 500 g batch and check your three numbers add up to 500.
