Bubble Wrap is made from polyethylene resin beads about the size of pea gravel. The beads go into an extruder (a long cylinder with a screw inside). As the screw turns heat builds up melting the resin into a liquid that is squeezed out into two stacked sheets of clear plastic film. One layer of the film is wrapped around a drum with holes punched in it, and suction is applied drawing one sheet of film into the holes forming bubbles. The second sheet is then laminated over the first trapping the air in the bubbles.