Ten Accidental Inventions That Changed Everything

In the late summer of 1928, Alexander Fleming, a bacteriologist at St. Mary's Hospital in London, came back from a vacation to a cluttered lab bench. One of his dishes of Staphylococcus bacteria had been contaminated by a mold. Near the mold, the bacteria were not growing normally. The date usually given for the discovery is September 28, 1928.

The accident took a remarkable chain of luck. According to the Science History Institute, the dish was never put in the incubator as planned, and the temperatures during his absence happened to let both mold and bacteria grow. How the Penicillium spore got there is unknown; a lab downstairs that grew molds is one possibility. Fleming's notes are sketchy and his later accounts conflict on some details.

Fleming published in 1929, but he could not produce the substance in useful amounts, and the paper drew little attention. In the late 1930s, Howard Florey and Ernst Chain at Oxford picked it up, and in 1940 they showed it could cure lethal infections in mice. With help from Norman Heatley's improvised production methods and later mass production in the United States, penicillin became the first great antibiotic. Fleming, Florey and Chain shared the 1945 Nobel Prize in Physiology or Medicine.

On November 8, 1895, the physicist Wilhelm Röntgen was experimenting with a cathode ray tube at the University of Würzburg. He had wrapped the tube in black cardboard to block its light. Yet a screen coated with barium platinocyanide, lying some distance away, began to glow. Something invisible was passing through the cardboard.

Röntgen was not looking for a new kind of radiation, which makes this a genuine accident of observation. What followed was not luck but weeks of methodical work. He found the rays passed through paper and even thick books, and that they could expose photographic plates. On December 22, 1895, he made an image of his wife Anna Bertha's hand, bones and ring clearly visible. He called the mystery rays X, for unknown.

His paper appeared at the end of December 1895, and the news spread with astonishing speed. Within a year, roughly a thousand publications on X-rays had appeared, and Röntgen received the first Nobel Prize in Physics in 1901. One caveat: his lab notes were burned after his death, so the exact sequence of that first evening is a reconstruction from his own later statements and those of others.

In April 1938, Roy Plunkett, a young chemist at DuPont's Jackson Laboratory, was trying to make a new refrigerant. He had stored tetrafluoroethylene gas in cylinders kept cold. When he and his assistant, Jack Rebok, opened the valve on one of them, nothing came out. Yet the cylinder weighed as much as when it was full.

Instead of throwing it away, they cut it open. Inside was a waxy white powder. The gas had polymerized on its own into polytetrafluoroethylene, or PTFE. Testing showed it was remarkable stuff: almost nothing stuck to it, acids did not attack it, and it held up under heat.

Its first major job had nothing to do with frying pans. The Manhattan Project needed materials that could survive the corrosive chemicals used to enrich uranium, and PTFE fit the bill. DuPont marketed it under the name Teflon, and nonstick cookware arrived much later. When Plunkett received a chemistry medal in 1951, guests at the banquet took home Teflon-coated muffin tins. The Science History Institute calls it an accidental invention, and the empty-but-heavy cylinder is the documented core of the story.

In 1968, Spencer Silver, a chemist at 3M, was trying to develop a strong adhesive, reportedly with aircraft construction in mind. He got the opposite: a weak glue that stuck lightly, peeled off cleanly and could be stuck down again. For about five years he talked it up inside the company, and almost nobody saw a use for it.

The use arrived in 1974. Art Fry, a 3M colleague who sang in his church choir, was frustrated that paper bookmarks kept falling out of his hymnal. He remembered Silver's adhesive and tried it on the bookmarks. They stayed put and came off without tearing the pages. Fry developed the idea further using 3M's policy that let employees spend some of their time on projects of their own choosing. Even the famous canary yellow was a fluke: it was the scrap paper a nearby lab happened to have.

Success was not instant. A 1977 test launch under the name Press 'n Peel flopped. In 1978, 3M flooded Boise, Idaho, with free samples, and people who tried them wanted more. Post-it Notes went on sale across the United States in 1980. Silver, who died in 2021, is credited as co-inventor alongside Fry.

In the 1830s, natural rubber was a bust. It turned sticky in summer heat and brittle in winter cold, and products made from it rotted. Charles Goodyear spent years and every cent he could borrow trying to fix it, and he was jailed for debt repeatedly over the course of his life.

The breakthrough came in 1839 at a rubber works in Woburn, Massachusetts. The popular version says Goodyear clumsily spilled a rubber and sulfur mixture on a hot stove. His own account, in his 1853 book on gum elastic (written in the third person), is a little different: he was deliberately testing the effect of heat on a treated rubber sample when it was carelessly brought into contact with a hot stove. Instead of melting, it charred like leather, and he realized that if the charring could be stopped at the right point, the result would lose its stickiness. The bystanders he showed it to were not impressed.

Goodyear himself bristled at calling it an accident, saying it came from years of close application and observation, and he compared it to Newton's apple. He patented the process in 1844, but he fought rivals including the English inventor Thomas Hancock and made little money. When he died in 1860, he owed about $200,000.

In 1956, Wilson Greatbatch, an electrical engineer at the University of Buffalo, was building a circuit to help record fast heart rhythms. He installed the wrong resistor: according to the Heart Rhythm Society, a 1-megohm part instead of a 10,000-ohm one. When he switched the circuit on, it began to pulse on and off in a steady rhythm, like a heartbeat.

Greatbatch realized that this kind of circuit, small and low-powered, could be built small and frugal enough with power to sit inside the body and keep a failing heart beating on time. In 1958 he teamed up with William Chardack, chief of surgery at the Buffalo Veterans Administration Hospital, and they implanted a prototype in a dog. In 1960, Chardack implanted the device in the first of ten human patients.

Greatbatch kept improving it. In the 1970s he developed a long-lasting lithium battery that stretched a pacemaker's life from roughly two years to about ten, which became the standard power source for implanted devices. He went on to hold more than 300 patents, but the pacemaker began with a part pulled from the wrong slot.

In June 1878, a chemist named Constantin Fahlberg was working in Ira Remsen's laboratory at Johns Hopkins University, studying compounds derived from coal tar. That evening at dinner, the bread roll he picked up tasted strangely sweet. So did his hands. He had not washed his hands well enough after a day at the bench.

Fahlberg went back to the lab and, in a move no safety officer would approve, tasted the chemicals at his workstation until he found the sweet one. It was benzoic sulfimide, far sweeter than cane sugar. He named it saccharin.

The accident is documented, but the credit became a feud. Fahlberg and Remsen published the compound together in 1879. Then in 1884, without telling Remsen, Fahlberg patented a cheaper way to make it and later promoted it as his own discovery. Remsen, who cared about recognition more than money, protested in print and never forgave him. Saccharin went on to boom during sugar shortages in both world wars. It survived a 1977 ban attempt after rat studies raised cancer fears, carried a warning label for years, and was cleared in 2000 when later research found the rat results did not apply to people.

Super Glue was discovered by accident twice, and rejected the first time. In 1942, during World War II, Harry Coover was working for Eastman Kodak on clear plastics for military gunsights. His team tried a family of chemicals called cyanoacrylates. They stuck to everything they touched, which made them useless for gunsights, so the team set them aside.

Nine years later, Coover was overseeing research at Kodak's Tennessee Eastman plant in Kingsport on heat-resistant plastics for jet airplane canopies. An assistant put a cyanoacrylate sample between the prisms of a refractometer, an expensive optical instrument. The prisms were glued together for good, and the instrument was ruined. This time Coover saw the opportunity: a liquid that bonded tightly, almost instantly, with no heat or pressure needed.

Kodak began selling it in 1958 as Eastman 910, and it later became known as Super Glue. During the Vietnam War, field medics used cyanoacrylate spray to slow bleeding from wounds, and the FDA later approved cyanoacrylates for certain medical uses. Coover was inducted into the National Inventors Hall of Fame in 2004 and received the National Medal of Technology and Innovation in 2010. He died in 2011 at age 94.