The extraction of the olive oil.

It's highly probable that the first elements of agricultural mechanization were made to produce olive oil. The extraction has indeed this particular: it uses exclusively mechanic means; we just need to extract a product that already exist in the natural state of the fruit, not to create a chemical process like it happens in the wine fermentation. We wouldn't be surprised if archeologists interpreted today several cavities, and some clubs as devices for the extraction of the olive oil from the Bronze Era in the Middle East and Crete (Eitam, 1987;Blitzer, 1993)

The olive oil extraction takes three steps:

• The grinding: to break the skin, and to squeeze the pulp;
• The pressing: to extract the oil from this accumulation of pulp;
• The decantation: to separate the oil from the vegetation water, solid elements and from the added water.

The antiquity contribution.

The extraction without the press.

It's normal when pressing with the hands some olives in a bowl with water, we could see surface some oil. The technique got improved with a simple millstone and adding hot water. It's the production of olive oil known as << the mortar>>, the Biblical olive oil, preferred for the sacred utilization and produced in small quantities. If the pulp, in small fragments, gets squeezed a first time with the feet, it improves the production. Often at the end, it is added some hot water to facilitate the decantation. It's an example the olive oil Zit Uberray still extracted in the XX century by the women in Kabiria. With the squeezing and the twisting, the olives are putted in a bag, and squeezed with the feet in a tub for the grinding. Then we put a stick to each extremity of the bag, and we twist like cloth that we put to dry. This technique was known in the Pharaonic Egypt, maybe for the oil, for sure for the wine (Montet, 1925;Meeks, 1923). It's confirmed in Venice and Spain in the Modern Era, and is still done in Turkey and in Corsica in the Contemporary Era (Casanova, 1990; Mattozzi, 1979; Gonzàlez Bianco, 1993).

The appearance of the revolving grindstone.

For a long time, the grinding has been made with a large stone directly moved by hand, or with wood sticks. From this comes the grinding cylinder that, in some cases, could be driven by an animal. The appearance of the perpendicular grindstone is very important, because is the first appearance of a revolving movement in a conversion device. Currently, the most ancient example is in the city of Olynthe, in the Northern Greece, of the IV century b. C. .The machine is presented as the <<trapetum>> described by Cato in the II century b. C. It is driven manually; there have been found several examples, of which one in Pompeii. It's a system that requires a very precise calibration: the grindstone chops the olives against the mortar's walls. They have to be very proportionate to its dimension. As matter of fact, there have been really quickly many kinds of perpendicular grindstones, the << Molae oleariae>>, with one or two grindstones that press on the walls or the bottom of the tub. These systems will spread out in the Roman period (Frankel, 1986-1993;Brun, 1986).

The appearance and the diffusion of the Press.

To lay down a stone on a chopped pulp and to wait for the pressure to naturally take effect is the simplest press. When they got the idea to hang the stone to a beam - the press shaft - that leaned on the chopped olives, it became a real machinery. Very soon we see appear in archeology these stones with a drilled track, the cupboards where they laid down the bags full of olives, the provençal diaphragm.
The presses could be classified (Parain, 1960) by the kind of pressure:

At angle;

At shaft;

• Simple counterweight;
• Fixed winch;
• A winch on the counterweight;
• A screw on the counterweigh;

As direct screws;

• As two screws;
• As one screw;

All these kinds will be known at the beginning of our Era and the Roman Empire correspond at an important diffusion of these devices in all the Mediterranean regions, proportionally with the growth of the demand and the production of the olive oil (Mattingly, 1988; Hitchner, 1993). It can be noticed some regional differences. One of the most important mechanic problems of these machinery was the risk of uprooting, in function of the pressure. The modality of shaft's housing were then changed: wood poles, the <<arbores>> of the Latin deeply interlocked, in Italy, stone monoliths resistant at the same weight, in Cyprus, in Dalmatia, in the Maghreb, for example. But also it have been interlocked the shaft in a wall, case that left less play for the oscillatory motion. When it could be used a troglodyte mill, they got the possibility of greater resistance, and the system was utilized in Lebanon, in Judea. (Callot, 1984; Eitam, 1987; Kloner Saguiv, 1993). The Angle press is showed in a painting in Pompeii; without any doubt it was needed (Mattingly, 1990) for the olive oil extraction to be used as a perfumes conditioner. The last improvement of the shaft's press was the screw. Interlocking a screw in the counterweight, they economized the work for the employees and increased safety. This system, that spread mainly in the Low Empire, was utilized a lot in the Middle Ages. Later will be improved with the utilization of spikes for the pressure ( Frankel, 1993; Amoureti Come Paillet, 1984). The direct screw presses appeared just before our era; these presses, though, won't take the place of the others. If it guaranteed a better control on the pressed oil, were more fragile and required a lot more service. Made with wood, it left fewer traces. It could have been with one or two screws and it probably spread out more then we think. So all the technical improvements were made in Ancient Times. In the Middle Ages and in the Modern Time just some aspects got improved. The Trapetum will fall into decay in favor of a bigger press, but the cylinder will remain. It improved the productivity of the shaft's press and tried to improve the dimensions of the direct screws.

The Decantation.

The olive oil being lighter then water floats on the surface and it can be picked up manually, or with a flat spoon, the patella. All the methods of decantation have been using the water. We can find the Greek big jar Pithoi, Roman Dolia, and the masonry tubs (Brun, 1993). The best basins are located in Northern Africa, with a sequence of communicating tub (Camps). It was very late, without any doubt in the XXI century of our Era, that it was felt the necessity to recycle the sansas and to obtain some more olive oil, of inferior quality. (Bernard, 1786; Magnan, 1985).

The XIX century changes.

The abbot Couture at the end of the XVIII century reminds that most of the direct producers didn't care about quality as much as quantity. the systems with very heavy shafts didn't give very high productivity. They tried to improve it with any means, like accumulating the olives for several days or boiling them, before putting them in the bags. It's interesting to notice that the Latin agronomists like Cato and Columella were worried about the olives and the olive oil quality. They recommended an accurate harvest without any beating down, a minute cleaning of the machines before and after using it and a rapid pressing after the harvest. These same attentions are suggested by the agronomist of the XVII and XVIII century. It then began a real campaign to improve the presses return and the olive oil's quality. It's the period when Corfù is covered up by olive tree cultivation and oil-mills (Sordinas, 1971), as it also happens in Italy; it's spreading out the direct screw press, while in France they are trying to improve its productivity, interlocking it in the vault. The agronomists are asking about some<< technical blocks>>.
So the agronomist Bernard puts in evidence the noble's reticence, of the press's owners, that look after the olive's quality, but are not interested to improve the pressing. Everywhere there were proposed improvements, like the winch to operate the screw. Some of these improvements weren't always practicable (Bella, 1784), but showed a great desire to improve (Amoiretti Comet, 1989). At the beginning of the XIX century, almost all of the pressing systems invented in Ancient Times coexisted: it's also found the torsion (or twisting), the chopping by mortar, the shaft presses and with simple counterweights, or a screws, or a direct screws. If the winch presses on counterweight disappeared for the olive oil, for the others remained. It's possible to see them coexist in the same town or the same region. They have in common the building materials like the wood and the stones, and this coexistence is not due only to the local habits, like is asserted too easily. Every system has advantages and inconvenient, and the change requires meditation. The changes of the XIX century and the beginning of the XX century brought a large expansion of olive groves in some countries: for example in Greece and in Tunisia. In the old olive growing countries like France, Spain and Italy, the olive growers are trying to gain terrain with the terraces. At the same time, it begins to appear the competition of the seed oils. The manufacturing of metal machines gives a big advantage to the screw press. Now with a smaller dimension, they've got a bigger resistance. The major problem, that was the risk of breaking, explosion and tearing under pressure, in part disappears. (Some shaft press built locally remained operating until the XX century). The fall of the manufacturing costs of the small press, in the second half of the XIX century, helps also its diffusion. But we can observe that even if there is an improvement, there isn't a technical change. We will need the arrival of the centrifuge, so that these machines invented in Ancient Times disappear after a very long use.

Conclusion.

Since the history of wine making techniques is often cited, the one regarding the methods of the olive oil extraction remained modestly on the sidelines (Amouretti Comet, 1989, 1993), even if is particularly important. It was because of the olive oil extraction that the first shaft presses got invented, the first vertical grinders, and perhaps, the first screw press. In a way we need to consider that it was conserved in the tasformation operations a certain number of simpler methods, some domestic, that went through the centuries. That's because they allowed compensating one of the majors inconvenient of the olive oil extraction, the one of irregularity of production, and the obligation to press very soon after the harvest. From this, the constant risk, never disappeared, of not being able to comply to the demand. The simple and domestic methods could go over this constriction, which remained inevitably for the speculative cultures. Finally, some kinds of extraction got preserved for religious tradition. And that's way once again that our technical history of the olive oil is linked to the social systems, at the mythical aspects and the economic role of this tree, which has its origins in the Ancient Times.