I was just reading a webpage about how things can become charged and it lists the mechanisms as charging by friction, induction and conduction. With charging my conduction there is an example that if a neutral aluminium plate is put into contact with a negatively charged foam plate, the charge will not move from the foam plate to the aluminium plate.
I was wondering why this is the case. I thought the obvious answer was because insulators do not allow the movement of electrons, but this foam plate is negatively charged so electrons have migrated to it. If they migrated TO it, why can't they migrate away to the aluminium plate