Conservators used mild chelating agents to lift the grime without disturbing the painted surface. Chelators are used in conservation to remove superficial salts and the tiny dirt particles attached to them. A low concentration of anhydrous citrate was included to remove the salts and dirt particles, while still maintaining a constant pH. A nonionic surfactant was also added to assist in large particulate soil removal. The cleaning solution was thickened with inert methyl cellulose. This allowed the solution to remain at a very low strength so that time itself would serve as the main variable during the removal of all dirt and surface grime. In this photograph a conservator from Parma Conservation applies the gelled solution to the Lincrusta with a soft brush.