Although the volume charge distribution in a homogeneous substance decays exponentially with time, in general this will not be true of the electric field above a free surface of the substance, due to the formation of surface charge. This must be taken into account in using the electric field or the surface potential as a measure of the electrification, or the decrease of these quantities as a measure of the time constant of a charged sample. The formation of surface charge during charge relaxation is considered in a simple one‐dimensional case. The contribution made by surface charge to the surface potential and electric field above the surface may be large if a grounded object, such as a probe or field meter, is near the surface.