Humbrol Weathering Powders are a versatile means of adding realistic weathering effects to your models, figures and dioramas. They can be mixed to create different shades, enabling a full range of finishes from dust to mud, soot, rust and many more. Usage Used to create realistic weathered effects. Substrate Weathering Powder can be applied to most substrates depending on the method. Application Weathering Powder can be applied dry or mixed with several Humbrol products. Drying Time Dependent of application methods. How to Clean Dependent of application methods.