A method of cleaning a contaminated surface, such as cleaning the elongate interior lumen of an endoscope contaminated with flesh, bone, blood, mucous, faeces or biofilm, said method comprising the steps of: providing a suspension of solid particles in a liquid to said contaminated surface, and flowing said suspension along said surface thereby to remove contaminant from the surface. The suspension is preferably a paste, where the solid material may be e.g. crystals of a salt, silicon oxide or organic material. The paste preferably has a solid fraction between 5 and 55%. A rheology modifier may be present.