The central compound of Silver's adhesive was an acrylate copolymer. But the adhesive was too weak and wouldn't stick for long. Acrylate polymers were a category of chemical compounds often used in paint, plastics and textiles. What Fry wanted was the perfect 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.