Resene Moss & Mould Killer is a highly effective hypochlorite-based cleaner that quickly kills and bleaches common mould and fungi on surfaces. It is recommended to use this product before repainting cementitious surfaces as mould growth is often present. Recognizing mould on painted surfaces can be difficult as it may appear like dirt. Mould is typically black but can also be brown or green. By wetting the surface and rubbing, mould will reveal itself as slime.