Spencer Silver, a longtime researcher at 3M Co. and co-inventor of its world-famous Post-it notes, has died.

Silver, who was 80, died suddenly from a heart condition last Saturday at his St. Paul home.

In 1968, just two years after arriving at 3M's research center and headquarters in Maplewood, Silver discovered a low-tack adhesive that could hold paper together and be removed and reapplied without damaging the paper.

"He was an artistic type of scientist," his wife, Linda Silver, said. "He looked at things in a different way and he had the freedom to go beyond."

Silver touted the creation, a microsphere adhesive formulation, around the company like a traveling salesman. But it sat on a lab shelf for six years before his colleague Art Fry thought of a use.

Company lore holds that Fry, active in his church choir, had an epiphany one evening in 1974 after becoming frustrated that his paper bookmarks kept sliding off the hymnal pages. He remembered a company seminar Silver had given on his special glue.

The Post-it Note, first named the "Press 'n' Peel" bookmark, was tested in four cities in 1977, but sales disappointed. The marketing team rebranded them "Post-its" in 1979 and rolled the product out nationwide the following year. Sales to Canada and Europe followed.

Today, Post-it Notes remain one of 3M's bestselling consumer products and a common product in homes and offices everywhere. The company declined to provide annual sales, but a market report estimates the global sticky notes market was worth about $2.2 billion in 2019, with 3M as the clear market leader.

Fry, the more extroverted of the two inventors, is often credited — including in pop culture references such as the 1997 film "Romy and Michelle's High School Reunion" — as the inventor of Post-its.

That didn't really bother Silver, his wife said, who was "much more an introvert and happy to sit back and let Art do the talking." And Fry was always quick to remind people that Silver created the crucial adhesive.

Silver earned 37 patents and won numerous awards, including the 1998 American Chemical Society Award for Creative Invention, induction into the National Inventors Hall of Fame in 2010 and Minnesota Science & Technology Hall of Fame in 2011.

Born in San Antonio, Silver spent his teen years in Phoenix before attending Arizona State University. He received his Ph.D. in chemistry from the University of Colorado at Boulder, where he met his wife of 56 years, Linda (Martin) Silver.

He was presented ample job opportunities around the country, Linda Silver said, but chose 3M for the creative flexibility he was being offered at the time.

He was quiet but had a sardonic sense of humor, Linda Silver said. When asked, he'd offer up ideas on little things like rearranging the furniture or what to serve at dinner parties — things that Linda Silver said she may not have thought of.

Silver took up painting in the 1990s, primarily focusing on abstract elements of nature, like flowers and trees. After retiring from 3M in 1996, he became more serious about his art, eventually taking a studio space in the Casket Arts Building and becoming an active participant of the northeast Minneapolis Artists Association. Silver often drew inspiration for his paintings from poetry, another art form he enjoyed.

The untimely death of his daughter Allison due to cancer four years ago was a singular event in both Linda and Spencer Silver's lives. His art evolved around that time, not toward despair or sadness but experiments in pointillism and swirls of color inspired by chemical reactions.

He loved cooking and watching YouTube chefs as well as taking his grandkids from California to northern Minnesota every summer for a wilderness experience.

He is survived by wife Linda, daughter Jennifer Silver, and two grandchildren, Zachary and Zoë. A memorial will be held at the end of July.