How to measure electrostatic charge in this scenario?

[24forChromium]

A block of aluminium is charged by a van-Graff generator and isolated in space, the goal is to measure the amount of electric charge in this block or at least a part of it. What equipment should be used and how?

Note: the purpose is to investigate how does the geometry of the block affect the concentration of electric charge in parts of the block, it is hypothesized that electrostatic charge is stronger in a sharp edge than in a flat side.

 

[jssamp]

By isolated do you mean not in the presence of an external electric field? Do you want net charge? On the surface, bound charges? The total charges on a microscopic scale would be the number of electrons and protons in the volume. isolated in no field the charge distribution is likely uniform as metals have electrons free to move. For charge distribution due to an external field you will have a surface charge distribution with no E field inside the block and the potential inside everywhere constant.