The most frequent cause of yellowing in dry cleaning is an excess color in the solvent. Solvents accumulate oils, greases, and dyes, resulting in a brown or yellow color. Fabrics with any tendency to retain solvent can yellow after extraction. Dyes in the solvent may have any affinity for some fiber types, in which case they can actually dye the fiber. In addition, some fibers can yellow at high drying temperatures. Still another cause of yellowing may be particles of iron rust from old metal containers used for storing chemicals.