Washing agents for museum textiles must be as safe as possible for the dyestuffs, the metallic mordants, and the fibers. Usual components of household detergents such as carboxymethylcellulose and polyphosphates should be avoided. Even surfactants must be restricted to weak concen-tration. Polyelectrolytes interact with dyestuffs, mordants, and flbers. They tend to remain on the textile, to change the colors, and sometimes, to form dangerous products after aging. A non-ionic surfactant ( Levapon 150-Bayer ) which can be used in very weak concentration (0.25 g for 100 liters of demineralized water) has been selected. Rinsing water is carefully tested with the foam test. The cleaning of old textiles must preserve museum pieces and not provide only transient renovation.