Electrochemistry Question, Galvanic/Daniel Cell

[mannioc3]

Using a very simple set up with high school kids,

Zinc Plate
*on*
Filter paper soaked in ZnSO4
*on*
cellophane
*on*
Filter paper soaked in CuSO4
*on*
Copper Plate
*in*
Petri Dish

Copper and zinc plate connected to a speaker. I know the process involved and the equations. Not using a salt bridge. After a while on the base of the Zinc plate there is a build up of a black substance and for the life of me i can't tell what it is.
Any ideas what it is?

 

[Borek]

I won't be surprised if it is copper reduced on zinc. It doesn't have to be red, at least not initially.

 

[mannioc3]

Where does the copper come from?
The cells are separated by the cellophane... how would the copper reduce and percipitate UP onto the zinc plate? is this possible?

 

[Borek]

If there is current flowing, it means ions pass through the cellophane, there is no other way.