 Luis Ruiz-Noguez believes that the most likely explanation for the visual effect of the Bélmez images is Jordán's suggestion of the use of an oxidizing chemical agent.For example, nitric, sulfuric, muriatic, acetic acid, and others, could be used to obtain such an effect.Another explanation might be the use of agents sensitive to light (which was not mentioned in either Jordán's or Perera's repertoire of forgery hypotheses)