Post-it Notes were invented in 1968 by a chemist named Spencer Silver trying to develop a super-strong aerospace adhesive — and the weak glue he accidentally produced instead sat unused for six years until a colleague named Art Fry needed something to anchor the bookmarks in his church hymnal

The man who invented the adhesive that holds together approximately 50 billion office notes per year spent six years walking around the 3M corporate campus carrying samples of his own discovery, looking for anyone — anyone at all — willing to find a commercial use for it. The compound itself was, by every chemical metric the 1968 adhesive industry recognised, technically interesting. The microscopic acrylic spheres Silver had synthesised possessed the unusual property of adhering to surfaces only at the points where the spheres made tangential contact — producing a bond strong enough to hold one sheet of paper against another but weak enough to allow the sheets to be pulled apart without tearing, and with the further property that the same patch of adhesive could be reattached and detached essentially indefinitely without losing its effectiveness or leaving residue on either surface. Silver was, in his own subsequent recollection, completely confident that the compound had substantial commercial potential. The 3M senior management, who controlled the company’s product development priorities, was substantially less confident. The adhesive was too weak for the aerospace application that had originally motivated its development. It was too weak for the heavy-industrial adhesives market that constituted most of 3M’s adhesive revenue at the time. It was difficult to package, difficult to apply, and difficult to characterise within any of the company’s existing product categories. Silver presented internal seminars on the adhesive at intervals across 1968, 1969, 1970, 1971, 1972, and 1973. He pitched it to product managers. He filed a patent on it (US Patent No. 3,691,140, granted in 1972). He earned, around the 3M central research laboratories, the nickname “Mr. Persistent.” Nobody could figure out what to do with his adhesive.

According to the Lemelson-MIT Foundation’s biographical summary of Art Fry and Spencer Silver and the development of the Post-it Note, the person who eventually figured out what to do with Silver’s adhesive was Arthur Fry — a 43-year-old chemical engineer in 3M’s tape division, who had attended one of Silver’s promotional seminars in 1973 and had subsequently filed away, in the back of his mind, the basic fact that the company possessed a strange weak-bonding compound with no obvious application. Fry was a Minnesota native, born in 1931, educated in a one-room schoolhouse in rural Owatonna, employed at 3M since his student years at the University of Minnesota. He was also a singer in the choir of the North Presbyterian Church in St. Paul, where he attended Wednesday-evening rehearsals followed by Sunday-morning services, and where he had developed the practical problem that would, in 1974, intersect with Silver’s underemployed adhesive: he kept losing his hymnal bookmarks.

The boring sermon

The specific moment of insight has, by Fry’s own subsequent accounts, become one of the more popularly retold episodes in late-20th-century corporate innovation history. Fry was at a Sunday service at North Presbyterian Church in early 1974, sitting in the choir loft, listening to what he would later describe (with a degree of clerical license he did not subsequently soften) as a “rather boring sermon.” His hymnal sat on the small wooden ledge in front of him. The slips of paper he used to mark the day’s hymns had — as they did most Sundays — slipped out of the hymnal during the choir’s standing performance of the previous selection and now lay scattered across the floor of the choir loft, requiring him to fumble through the hymnal to find the next selection. He had been having this problem for years. He had, by his own account, never found a satisfactory solution. As the sermon continued, Fry recalled the strange weak-bonding compound that Silver had been promoting at internal 3M seminars across the previous six years. The connection clicked. What if the bookmarks themselves were treated with Silver’s adhesive? They would stick to the hymnal page. They would not damage the paper when removed. They could be repositioned to mark different hymns each week. They would not fall out.

Fry returned to 3M the following morning. As detailed in the National Inventors Hall of Fame’s account of the Post-it Note’s collaborative invention by Silver and Fry across the 1968-1980 period, Fry’s initial prototype was technically problematic. The adhesive that Silver had synthesised did bond strongly enough to function as a bookmark, but the initial paper substrate Fry used did not bond strongly enough to the adhesive itself — meaning that when the bookmark was peeled off the hymnal page, the adhesive stayed on the page rather than on the paper, leaving residue and rendering the bookmark single-use. The engineering problem was solved across the subsequent three years by two other 3M chemists — Roger Merrill and Henry Courtney — who developed a primer coating that bonded the adhesive permanently to the paper substrate. The paper itself was supplied, almost by accident, by an adjacent 3M laboratory that happened to have a stack of unused canary-yellow scrap stock in its supply cabinet. The yellow colour that would, four decades later, become one of the most globally recognised office-supply visual identifiers had been chosen because it was what the adjacent lab had available to spare.

How a product nobody wanted became a product nobody could function without

The commercial launch was, by every available measure, initially disastrous. As reported in a Today I Found Out reconstruction of the Post-it Note’s protracted commercial development, 3M conducted a limited four-city test marketing campaign in 1977 under the product name “Press ‘n Peel.” Consumer response was lukewarm. People who saw the product in stores did not understand what it was for. The packaging did not adequately explain the use case. The product appeared to be a solution in search of a problem. 3M’s senior management, having spent nine years tolerating Silver’s adhesive and three more years developing the paper version into a marketable product, prepared to discontinue the line. The intervention that saved the Post-it Note was a 1979 follow-up campaign — known internally as the “Boise Blitz” because it was launched in Boise, Idaho — that distributed massive quantities of free samples directly to administrative assistants and office managers at businesses across the test city. The hypothesis was that the product was self-demonstrating: once anyone actually used a Post-it Note in their day-to-day office work, they would understand the application immediately, and would generate further demand through visible use of the product in their interactions with colleagues elsewhere in their organisation.

The hypothesis turned out to be correct. As described in the official Post-it Brand corporate history maintained by 3M on the product’s development from 1968 through subsequent decades of commercial success, 90 percent of the Boise office workers who received free samples reported that they would purchase Post-it Notes once the product became commercially available. The national US launch followed in April 1980. The success was immediate. Within two years, Post-it Notes had become one of 3M’s largest single product lines. Within a decade, the product had been launched in essentially every developed market globally. Spencer Silver was eventually inducted into the National Inventors Hall of Fame in 2011, alongside Art Fry, in a joint recognition of the original 1968 adhesive synthesis and the 1974 bookmark application that had, between them, produced an office supply product currently sold in more than 100 countries and used (by one industry estimate) approximately 50 billion times annually. The compound that Silver had originally been hired to make in 1968 — the strong aerospace adhesive that he had specifically failed to produce — was eventually developed by other 3M researchers across the subsequent decades and is now used in various commercial bonding applications that the company does not particularly publicise. Silver himself, who continued working at 3M until his retirement in 1996, spent much of his later career as an accomplished amateur painter in pastels and oils, and died in St. Paul in May 2021 at the age of 80. His failed aerospace adhesive remains, on the available evidence, the most commercially successful chemistry-laboratory mistake in 20th-century industrial history.