In June 1752 Ben Franklin conducted what is called his “kite experiment” that proved lightning was electrical in nature. He famously did this by flying a kite in a thunderstorm with a metal key tied to the kite line. The idea sounds a bit dangerous and Ben, indeed, is usually shown cavorting in a field as lighting cracks all around him. In reality, the wily Franklin wasn’t quite so willing to sacrifice himself for science. And hemp cordage was part of both his personal protection and electrical sensing system.

Rather than standing out in the open where his body could have been struck, Ben actually picked a field that had a shed or lean-to on it. He stood in the shed, which protected him from a direct strike. The kite line extended out the open end of the shed.

The kite line itself was made of hemp cordage, which can soak up water and be very conductive of electricity. To protect himself from getting a shock from the hemp line, he tied a length of silk cord to the end of the hemp line and held onto that. While not strictly an insulator, silk is less conductive than hemp, so this provided Ben with some protection from a surge of current coming down the line. Where the hemp and silk were joined, Ben tied in the metal key.

But how did the hemp cord assist Franklin in his experiment?

Ben, ever the keen observer, took note that when the storm was overhead and lighting was present, the thin fibers along the outside of the hemp cord became electrically charged and stood straight out, like your hair can stand up when charged. When Ben saw that he knew that cord was charged with electricity. Then he brought the knuckle of his index finger close to the key and a thin spark jumped from the key to his hand.

A little hemp and Franklin was flying! He had proven that lightning was an electrical discharge.