Von Guericke noted this, but failed to explain it satisfactorily.

Dufay, repeating Von Guericke's experiments, found that if, while the excited tube or sulphur ball is driving the repelled feather before it, the ball be touched or rubbed anew, the feather comes to it again, and is repelled alternately, as, the hand touches the ball, or is withdrawn.

From this he concluded that electrified bodies first attract bodies not electrified, "charge" them with electricity, and then repel them, the body so charged not being attracted again until it has discharged its electricity by touching something.
"On making the experiment related by Otto von Guericke," he says, "which consists in making a ball of sulphur rendered electrical to repel a down feather, I perceived that the same effects were produced not only by the tube, but by all electric bodies whatsoever, and I discovered that which accounts for a great part of the irregularities and, if I may use the term, of the caprices that seem to accompany most of the experiments on electricity.

This principle is that electric bodies attract all that are not so, and repel them as soon as they are become electric by the vicinity or contact of the electric body.

Thus gold-leaf is first attracted by the tube, and acquires an electricity by approaching it, and of consequence is immediately repelled by it.