Term utilized in reference to a phenomenon that attacks the surface of paintings and that may depend on various factors. Most frequently, blanching is provoked by humidity that causes small cracks in the paint creating a milky appearance until the painting is rendered illegible (see bloom). The term is used in relation to the phenomenon provoked by mold and for mural paintings, by saltpetre. In relation to the cause, the restoration foresees diverse methods to resolve the inconvenience, from the use of fungicides to the removal of varnishes or to their regeneration (the Pettenkofer process).