In this work a measurement of the total amount of liquid metal created by an electric arc in air is made for copper anodes. Measurements are presented for various values of the arc current intensity in the range [200 A - 1000 A], electrode gaps in the range [3 mm - 10 mm] and arc durations in the range [5 ms - 20 ms]. Comparisons with usual erosion rates obtained in similar experimental conditions are made. Moreover, a numerical modelling of the heat conduction (taking into account phase changes) has been used in order to characterize the power balance (power and surface power density) at the electrode surface.