The Vallejo Weathering Effects range, have been formulated with permanent pigments and water-based acrylic resins, have been developed to represent the effects of time and weather on models and dioramas.

Brown Thick Mud is a dark colored mud, typical of fertile clay lands where humidity is retained during long seasonal periods, found mostly in Mediterranean areas and the west of Europe. Different from Vallejo Brown Splash Mud, this Weathering Effect gives the apperance of thick, sticky mud.