This paper deals with an experimental and theoretical study of the influence of copper vapours on the properties of a arc plasma. Spectroscopic measurements in pure plasma and in a -copper mixture in which copper was provided from the erosion of the anode have been realized. Temperature and relative copper concentration profiles determined experimentally were compared with theoretical values obtained from a two-dimensional physical model. This comparison validated partially the model and the transport coefficients calculated by our team and used in the model. The results showed that the effect of the presence of metallic vapours with a relative concentration of about 1% is too weak to induce noticeable modifications of the properties of plasma. However, a significant cooling of the plasma is calculated for a copper concentration of about 10%.