An electron beam projected onto a clean glass surface in vacuum is blown up by deceleration caused by the high surface charge accumulated, thus spreading the beam on a very short time scale before arrival on the surface. Arriving at the surface, electrons are rapidly bound to lattice imperfections (not adsorbed gas atoms) presumably creating O− ions. Thereupon, spread of the charge along and through the surface, progresses by movement of labile alkali ions which combine with the surface O− ions, leaving their initial negative O− partners behind in the glass. The rapid transfer of the negative charge from the surface to the interior of the glass, where it encounters dielectric screening, causes a temporary positive displacement current which masks the displacement current due to the discharge movement to the grounded electrode. It has a maximum value immediately following the electron beam cutoff, and declines approximately exponentially with a time constant τ, of about 0.1 sec for the range of electron surface charge densities, computed from beam cross sections ranging from 1010−3×1011 electrons/cm2. Thereafter, the charge leaks off as a volume conduction current on a time scale of tens of minutes. There is no surface conduction by free electrons, and surface conductivity of clean glass is low and comparable with volume conductivity. High apparent plasma induced surface conductivity lies in the plasma, and not in the glass.