A whiteboard or other surface has sensors located with respect to the whiteboard or opaque surface so that interaction with the whiteboard or other surface with a writing implement is detected by the sensors located beneath the surface. The electrical properties of the inks interact with the signals transmitted and received by the conductors. These changes are measured and used to reproduce marks made by the writing implements, to store the marks made for later reproduction, or to display contemporaneously with the writing upon the surface.