Optical spectroscopy of the emission from a plasma created during electrical discharge machining (EDM) showed a strong Ha line coming from neutral hydrogen atoms and continuum radiation. An electron temperature of 0.7 eV and plasma density of 2.1018 cm(3) had been calculated. New spatially-resolved as well as temporal optical emission spectroscopy of the EDM plasmas showed that this density is slightly higher in the plasma center and decrease rapidly with time. The electron temperature remains roughly constant across the plasma. Analysis of the pre-breakdown duration shows that the breakdown mechanism in water may be different from the one in oil.