An aqueous treatment composition for ITM (Intermediate transfer member) of a printing system and a method of printing comprising the step of applying said treatment composition to the surface of an ITM, wherein said treatment composition comprising: at least 3% wt quaternary ammonium salt, at least 1% wt water soluble polymer, and at least 65% wt water. Also disclosed, a printing system comprising a an ITM and treatment station for forming a thin layer of liquid treatment formulation on the ITM surface.