Conall
The extraction of oil from olives has always been done in two phases: first the crushing of the olives and then the separation of the oil from the olive mass and then from water.
At the time of the Egyptians, primitive mortars were made of a stone quarry in which olives were pounded with the help of a large stone by pouring in some cases the liquid in adjacent cavities. Later, the paste thus obtained was pressed with the help of a dense crown of live branches under the weight of heavy rocks. The oily must was collected and poured into earthenware jars, where the oil would separate from the water. Sack-shaped presses represented another, slightly more evolved, separation method. The olives were pounded inside robust canvas bags and then twisted with the help of two sticks. These were either inserted through loops made on the two ends of the bags or the bag was attached to a rigid frame by a side so to apply force to one end only.
Another extraction technique was realized with the introduction of the lever press. Under the weight of large rocks, the beam pressed on the discs containing the minced olive paste. Then, the oil was pumped into containers through channels carved into the stone.
Between VIII-VI B.C. olive cultivation started in Greece. The Greeks were already familiar with an olive grinding method that was much more effective than simply beating olives with stones. One or more large millstones, attached to a central pole, rotated around a round tank thus chopping olives.
Different authors who all note the great attention to cleanliness describe the oil production technology in Ancient Rome. The oil extracted with various type of presses was collected through receptacles underneath the press or conveyed directly into the receiving containers. Through subsequent decanting, the sludge was eliminated at times adding toasted salt to avoid freezing.
In the sixteenth century, there was a revival of olive tree cultivation following a period of relative peace after barbarian invasions. In Tuscany, the harvesting was done through tree stripping, while in Puglia olives were collected thanks to a cloth lying under the tree. The eighteenth century was the golden age for the revival of olive oil production technology. The use of copper instruments was banned because of oxidation while wooden ones were difficult to clean. During the nineteenth century, olive oil was still used predominantly in cities and by wealthier people. Documents show that already in 1800s ways of fermenting olives in piles were already known. Rising labour costs also pushed towards more practical and efficient machines. It was during this period that presses with two screws are replaced with those with one screw also in the South.
The early twentieth century spread the use of oil mills like ‘stables’ where the press was pushed by the movement of an animal running in adjacent room. The presses were made of metal with a mechanism to reduce friction. The pumps that put in motion the hydraulic presses could be operated either by hand or mechanically.
