The central compound of Silver's adhesive was an acrylate copolymer. But the adhsive was too weak and wouldn't stick for long. Acrylate polymers were a category of chemical compounds often used in paints,plastics and textiles. What Fry wanted was the perfact pressure-sensitive adhesive.He experimented with particles called microspheres, tiny round molecules.When sprayed onto a surface,the adhesive coating was just like the pebbled surface of a basketball. By spraying the adhesive in the form of these round microspheres,he could coat a surface that wasn't too sticky or too weak.This allowed a post-it note to stick onto the page of a book, but it could later be easily removed and stuck again somewhere else.Conversely,normal packing tape had a flat surface,hence allowing it to stick permanently