Efflorescences identified as acetate salts were found on over 150 ceramic objects in a museum in Belgium. The objects were treated by salt concentration reduction. An investigation was undertaken into the exact causes of the damage. Analyses were conducted of efflorescences, was solutions, air pollutants and display-case materials. The relative humidity and temperature inside and outside the cases were measured over one year. The importance of the location and nature of the salts and implications for the active and preventive conservation of ceramics, or other calcareous museum objects, susceptible to similar damage are discussed. -- MCI