A high-temperature process in which powdered materials below their melting point are compacted together to create a solid form. The process is based on atomic diffusion in which atoms in the powder particles diffuse across the boundaries of the particles, fusing the particles together, and creating one solid piece. Since the materials are not required to reach their melting points, the process is useful for materials with very high melting points such as tungsten (m.p. 3,422^ºC). Virtually all metals can be sintered, as can many non-metallic substances such as glass, ceramics, and organic polymers. Sintered bronze is used in bearings since its porosity allows lubricants to be retained within it. Sintered stainless steel and porous plastics are used as filter materials employed in the pharmaceutical and food industries. Sintered powders of silver and gold are used to make jewellery.