Initially, olive oil was produced in households. Each family produced the quantity of olive oil it would need - to this end, they used stone vessels (mortars) where the olive fruit was simply crushed and heated. With the development of the first olive mills, the olive fruit was manually crushed. Olives were placed on large stone plates where pressure was exercised by a round-shaped stone. Then, olive paste was transported to the presses. The base of a press was a large, shallow basin made of stone, of a round or rectangular shape. Pressing took place with the use of a stone weight that was placed in the edge of a wooden beam, which was pulled downwards.
In the Helladic area, during the classical era, the cylinder crusher was introduced. In the Hellenistic period, the olive fruit was crushed with a rotary mill. The rotary mill is a type of olive mill called 'trapetum' (a word of Greek origin, from the Greek verb 'trepo', which means 'turn').
This type of olive mill consisted of two millstones with curved external surfaces. The millstones were rotating with the help of thick beams with a rectangular cross section and were grinding the olive fruit.
In Roman times, a new type of olive mill was introduced that was known as 'mola olearia'. This olive mill consisted of one or two cylinder-shaped millstones, which were usually supported by a large vertical axe. In a different type of olive mill, a millstone was used which was supported by an iron pile.
In Byzantine times, both the 'trapetum' and the 'mola olearia' were used.
With the industrial revolution of the 18th century AD in Europe, olive mills were equipped with machines.
In Greece, olive mills began getting equipped with machines of foreign and Greek machine shops in Piraeus and other urban centers at the late 19th century.
Four olive mill types are recorded. The first type was the 'pre-industrial, animal-drawn' olive mill that was predominant in Greece until 1970. Metal presses, winches and other metal components were mounted on that olive mill. The second type was the 'pre-industrial water-powered' olive mill, which was already known from the Byzantine era. This type was widely used from the 10th century AD, with water serving as its power source.
Water moved a large wheel with blades, which, combined with cogwheels and belts, set the mill in motion. The third type is the steam-powered olive mill. The mill moves based on steam power. The first steam-powered olive mill in Greece appeared in 1870. The last and most advanced type is diesel-powered olive mills.
They made their appearance in the 20th century and diesel was used to power their machines. In this type of olive mill, the mill floor is made of iron and millstones are made of a harder stone whereas presses operate on water power.