Spencer Silver Invented an Adhesive No One Wanted for Twelve Years

US3691140 was filed on March 9, 1970, and granted to Spencer F. Silver of 3M on September 12, 1972. The title is "Acrylate Copolymer Microspheres." The text describes a polymer adhesive composed of tiny acrylate beads, each one about the size of a single skin cell. When the bead-coated surface contacts another surface, the beads adhere lightly — strongly enough to stay attached, weakly enough to peel off without leaving residue, without tearing paper, and repeatedly. You could stick the material, peel it off, stick it again, and the beads would not have lost their adhesion.

Silver had not been trying to invent this. He had been working in 3M's central research lab on a project to make a stronger adhesive for the aerospace industry — something that would hold airframe components together more reliably than existing glues. The microsphere result, which he stumbled into in 1968, was a failure by every metric that mattered to that project. The beads did not bond permanently. They had roughly one-twentieth the holding strength of conventional contact adhesive. They were, by any reasonable measure, unfit for any of the applications 3M was actually trying to address.

A solution in search of a problem

Silver was, however, completely fascinated by what he had made. The reusable peel-and-stick property of the adhesive seemed to him obviously useful for something, even though he could not say what. He spent the next several years giving informal seminars on the technology inside 3M, hoping that someone in product development would recognize the application he had failed to think of. The seminars became something of a running joke in the company. People would attend, listen politely, admire the adhesive, and then go back to their actual work with no idea what to do with it.

The patent issued in 1972. The product line implied by the patent did not exist. There was no obvious customer.

The hymnal

In 1974, six years after Silver's accidental discovery, a 3M new-product researcher named Art Fry attended one of Silver's seminars. Fry was a singer in his church choir, and he had spent most of the previous Sunday struggling with paper bookmarks that kept falling out of his hymnal during the service. Sitting in Silver's seminar, he had the connection: the adhesive Silver kept showing in those slides was the perfect bookmark glue. It would stick to the page during the service and peel off without tearing the hymnal when he was done.

Fry began making prototype sticky bookmarks at his desk. Within a few weeks he had realized that the application was much larger than bookmarks: anywhere people might want to leave a small temporary note, the same product would work. He began carrying prototypes around 3M's offices and giving them to colleagues. Demand was immediate and visceral. Once you tried one, you wanted more.

3M's marketing department, however, initially refused to commission a product. Focus groups did not understand what the adhesive paper was for. Sales projections were weak. The marketing leadership concluded that there was no consumer market for it.

Fry persisted. He insisted on a trial release in a single market — Boise, Idaho — in 1977. Demand among Boise office workers was overwhelming. 3M expanded the trial. Demand expanded with it. In April 1980, twelve years after Silver's accidental discovery, Post-it Notes shipped nationally.

What it became

3M still does not separately report Post-it Note revenue, but external estimates put the brand at well over a billion dollars in annual sales by the late 1990s and into multiple billions today. The product is one of the most successful consumer office goods of the twentieth century.

Silver, who had made the adhesive in the first place, received a 3M research-grade share of the royalties under the standard inventor-compensation agreement. He retired from 3M in 1996 and died in 2021 at age eighty. He was, by every account, philosophical about the twelve-year gap between his discovery and its eventual market success: the invention had been ready; the application was the slow part.

See the original

The full text and figures of US3691140 are on patents.us.