In 1988, five paintings by Albrecht Dürer in the Alte Pinakothek, Munich, were seriously damaged by an attack with sulfuric acid. First attempts at cleaning showed that this would involve additional loss of original material. Since all the affected areas registered a pH between 1 and 2, thorough neutralization of the damaged portions seemed unavoidable. After experimenting unsuccessfully with wet chemical neutralizing solutions, it was decided to use the ion-exchange method. The ion-exchange resin was preconditioned in the laboratory and applied to the damaged areas in the form of a watery paste, working under a microscope. After drying overnight, the powdery compound was removed with a mini vacuum cleaner. This treatment was in most cases sufficient to reduce the acidity level to a moderate pH of 6 or 7. It was then necessary to consolidate the damaged areas. Partly because of the enhanced porosity of the exposed ground layer, and also to avoid unnecessary rewetting of the affected parts, a mixture of beeswax and dammar resin was chosen. A traditional wax-chalk filler will be used before retouching.