When rice is harvested it has a non-edible hull or husk which surrounds the kernel. At a rice mill, all straw and other foreign material is first removed from the rough rice by a series of machines.

Then the rough rice is passed through "sheller" machines, which remove the hull and expose the brown rice, with the bran layers still surrounding the kernel. The brown rice is then "milled" by machines, which actually rub the grains together under pressure to remove the bran layers, by abrasion.

The primary objective in milling rice is to remove the hull and the bran layers while preserving as many of the whole kernels as possible. In spite of the extreme care used, there is some breakage of kernels. The amount of breakage depends on many factors such as the nature of the grain, its shape, weather conditions under which it was grown and the amount of pressure applied to the grain in the milling process.