Pressing the Olives at the Traditional Mill

After the olives have been picked they are brought to the mill for pressing. The first step is to unload them into larger crates whose weight is known. The total weight is recorded, and the weight of the crates is subtracted. The mill provides a first receipt with this information.

The crates are then emptied onto a conveyor, which carries the olives on stainless steel rollers up and inside the mill, where they pass through a cold-water bath. This removes all remaining traces of soil and leaves.

The conveyor then moves the olives to a large basin holding the two giant stone wheels that will crush the olives into a paste. As the wheels turn, they circle around the basin, forcing the paste to the perimeter, where large spatulalike attachments constantly keep it gathered it for the next step.

From the basin, one worker scoops the paste onto a large trowel and slathers it onto large glass fiber pads, which another worker then sets on a spindle. When the spindle has about thirty to forty pads, it is rolled over to the hydraulic press.

The spindle and the pads are set beneath the press, and gentle hydraulic pressure from below forces the oil out of the paste. The oil passes through a conduit to the centrifuge, which separates the water from the oil. Finally, the oil pours from a spout into a container, which has been carefully cleaned with vinegar beforehand. As each container is filled, it is closed and another is put in its place.

The pads are then cleaned, and the solid oil cake is deposited outside the mill, from where it will be hauled away as waste. The process is repeated many times each day.

When you come for your oil, the mill provides you with a final receipt showing the cost of the pressing, the weight of the olives, the quantity of oil, and the percentage yield, which can be a good indicator of the health of your grove. In a good year, the yield can be as high as 21 or 22 percent. In a typical year, the yield is around 17 or 18 percent.