- Rice polishing machine
Machine for removing the pericarp and surface layers of brown rice (genmai) to make white rice (hakumai): the process known as rice polishing (sei-mai). There are two kinds, the “horizontal grinding” apparatus used mainly for the polishing of eating rice, and the type of machine arranged on a vertical axis, which was developed for brewing use.
“Vertical” rice polishing machines operate by grinding away the outer portion of the rice with a round, rotating millstone (commonly called the “roll”, ロール,) made of emery or other extremely hard minerals.
The rice drops from a tank at the top of the machine, and a resistance plate at the exit of the polishing chamber is used to limit the rate of flow. This causes rice to accumulate in the chamber, and it is pressed against the millstone to be ground down.
A vibrating sieve where the rice leaves the polishing chamber separates rice powder from the remaining rice grains, which are carried by bucket conveyor back to the top of the machine to begin the process again, and polishing proceeds as the rice repeatedly travels through the polishing chamber.
The size of a machine is indicated according to the size (in inches) of the millstone. A machine with a 16 inch (40cm) “roll” is called a ju (long “u”) -roku gata (16型: a “model 16”), and there are also 18, 20, 22, 25 and 26 inch sizes, with relative capacity (where 16 inches =1) of 1.5, 2, 3 and 3.5 respectively.