Minute silver cubes were treated with cationic gold which at room temperatures led to a loss of electrons from the silver atoms which were taken up by an electrolytic solution. The gaining of electrons transformed the cationic gold into metallic gold which then attached to the surface of the silver cube. This covering protects the underlying silver, confining the reaction to the uncoated parts. Finally, there remains only a single hole on the surface through which the reaction enters the cube. A secondary effect then takes place when silver atoms from inside the cube begin to migrate through the hole to the gold on the surface, creating a void inside the cube.