Intensity is controlled by a combination of bead size and velocity. Glass is a brittle material when compared to steel. Hitting a glass ball with a hammer will fracture it but that wouldn't happen with a steel ball. Glass beads are useful for softer target materials such as aluminum alloys. Have you read article 1990149? This can be accessed from the Shotpeener.com library, enter "glass beads" in the Search box and this article is the fourth one down. The article provides an excellent background of knowledge.
