The final dry milling and selection takes place when our roastery calls for another sack of coffee to roast, or we are preparing to export a shipment of green (unroasted) coffee. The parchment is peeled by a machine which uses friction to rub off this outer layer. Then the coffee is sorted. The denser the bean the higher the quality. Therefore, you can use wind to sort coffee. The catadora or first sorting machine uses a fan to blow coffee upwards within a hollow tower. The lighter (lower quality) coffee reaches a higher point before falling out of the tower. The coffee can then be run over the surface of a vibrating table which sorts the beans by density and shape. The final selection is done by electronic sorter. At this point the coffee is sorted for color. Each bean falls through a thin column, one at a time. The sorter uses light refraction to compare the color of the bean to a background. If it is the same the bean falls through, if it is different it is blown out with a jet of compressed air. Sounds complicated and time consuming, but these sorters work at a speed of 600 beans per second! Previous | Beginning | Next