In the plating of non-conductive substrates, a metal-salt solution for treatment of such a substrate having been treated with a metal colloid for activation, and associated method for coating non-conductive substrates, characterized by reduced incrustation the associated equipment; the metal-salt solution comprising a metal that can be reduced by the metal of the metal colloid, a complexing agent, and a metal salt having a metal of the group consisting of lithium, sodium, calcium, rubidium, and cesium in the form of a salt selected from the group consisting of fluorides, chlorides, iodides, bromides, nitrates, sulphates, and mixtures thereof.