Around 1745, the German scientist Johann Heinrich Winkler demonstrated the effects of static electricity by electrifying his assistant, who was then handed a glass of brandy. As soon as he lifted the glass to his mouth, sparks would fly from his tongue and set the brandy on fire. The popularity of such performances, and the unexpected effects related to electricity, triggered the invention of various electrical friction machines—for private and public use—throughout the 18th century.
The core feature of almost all of these devices was a piece of revolving glass that rubbed against fixed pads, thereby creating an electrical charge.
The pads are connected to a cylinder-shaped negative conductor, while a hemispherical positive conductor almost touches the glass disk. The most conspicuous feature of this machine, an invention by the Austrian scientist Georg K. Winter, is the large wooden ring, which originally had a thick wire running through its center. The device did not aim for accumulating particularly high charges, but rather to generate long and dense sparks. Together with additional devices, such as a Leyden jar (a condenser that was invented in 1745), it probably served as a teaching tool for high school and college students learning about physics.