in my physics lab we did an expirement where we had to use an vernier electrostatic kit. So it consisted of placing a metal can inside a metal cage, and both were attached to an plastic disk, and below was a metal plate which was used for grounding. A black wire was connected from the cage to the metal plate, and a red wire was attached from the metal can to a charge reader, which was connected to a laptop to read the charges. I also had a blue wire in my wrist and it was also connected to the metal plate, for grounding. my question is this, we rubbed two charge seperators, one white and one gray, and we put the white seperator inside the can, resulting in a positive reading. And then i touched the metal can with my finger resulting in a negative reading (my teacher said that we did something wrong it should have a reading of 0, but that is not important, we only have to explain what happened). Then i released my finger from the can, and nothing happened. then i released the white charger from the metal can, and the reading become more negative, but why? where did the extra electrons came from at end phase?