After rice has been harvested, it is threshed to loosen the hulls, traditionally by flailing, treading or working in a mortar and winnowed free of chaff by tossing it in the air above a sheet or mat. If harvested using a combine harvester, this machine will also thresh the grain.
Once sold, the rice, known as paddy or rough rice is screened to remove stones, loose chaff and paddy stalks (part of the plant). The rice is then slowly dried by warm air to reduce any moisture. It is then screened to remove dust particles. Once cleaned in this way, it is ready for milling. In the first stage of the milling process the outer husk is removed, but the remainder of the kernel including the bran layer is left intact. At this stage the rice is known as cargo or brown rice. It is then cleaned and graded. If the brown rice is to be sold as white rice it then proceeds to the second stage of the milling process, an abrasive action which removes the bran layer surrounding the rice grain. Some grains are broken in this process. These are known as broken rice and used as ingredients for a wide range of foodstuffs either as they are or ground into rice flour.
In the US, most parts of Europe and increasingly elsewhere, the cultivation and harvesting/processing of rice has undergone the same mechanisation as other grain crops, lessening the overall labour required to produce it. However, mechanisation is more difficult to achieve in systems where rice seedlings are transplanted into paddy fields rather than sown directly as seeds.