Although our knowledge of the chemical mechanisms of the decomposition of paper caused by copper pigments is still incomplete, some important conclusions can be drawn. The discoloration and the loss of mechanical properties of paper is a result of the oxidizing action of soluble copper compounds. The presence of acidity plays an important role. An acidic environment accelerates the decomposition reactions. Nevertheless, deacidification alone will not stop the decay unless soluble copper compounds are removed from the object or converted to chemically inert compounds.