The two long parallel lines are long electric belts about 3/4 inch apart. Bottom belt is carrying sand or abrasive that has been ground to give sharp edges. Top belt is paper with glue coating on bottom of paper.
Passing through electric field of 40,000 to 50,000 volts makes the sharp edges of abrasive point outward as glue holds the base of particles.
May be a high voltage abrasive idea to some experimenter?
