Powder coating is a type of dry coating, which is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electro statically and is then cured under heat to allow it to flow and form a "skin." The powder may be a thermoplastic or a thermo set polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as "white ware", aluminum extrusions, and automobile and motorcycle parts. Newer technologies allow other materials, such as MDF (medium-density fiberboard), to be powder coated using different methods.