A method of direct dating rock carvings and engravings, potentially applicable to Paleolithic artifacts with a strong patina caused by exposure to desert dust. The technique is based on the principle that cations of certain elements are more soluble than others; they leach out of rock varnish more rapidly than the less soluble elements, and their concentration decreases with time. A cation is an ion carrying a positive charge which moves toward the negative electrode/cathode during electrolysis.