The occurrence of discoloration of natural ultramarine, called ultramarine sickness , on traditional paintings is generally known. Although it has never been fully investigated, ultramarine sickness is usually explained as the result of exposure to acid. Recently, discoloration of synthetic ultramarine has been noted on a number of paintings by contemporary Swiss artists. In the case described, a loss of binding medium was found as a possible cause for this change in color. Infusion with additional binding medium is being attempted as a remedy.