MIT Physics Demo - Dissectible Capacitor

[Bunuel66]

I have read across the web a lot of complex explanations of this demo. IMHO the explanation is very very simple. Charges are stored at the surface of the glass, the two copper cylinder being fully conductive and creating an electric transverse field charges move accordingly and create a potential difference. There is no spark through the glass as its conductivity is much too low. When the experimenter reduce the gap in air a corona discharge occurs. Then when removing the cylinders the charges remain on the glass surface and the copper (after being removed) is just at the same potential than the experimenter. This is valid for both cylinders. Then after being removed those cylinders are no more than copper electrodes in air. When reassembling the copper cylinders with the glass, they regain the potential of the glass surface with which they are in contact. The glass can be manipulated by the part not being between the copper cylinders as it is non conductive and no difference of potential exists in the upper part (you can manipulate a wire under voltage with an isolator). What would be interesting would be to put a wire bounding the two surfaces of the glass (without the copper cylinders), if my theory is correct a spark should still occurs. In other words it is just like connecting two electrodes to an electric cell showing there is a dop between them, disconnecting the electrodes and showing that there is not any more any dop, then reconnecting them and showing that the dop (of the cell) between them is back...