The quantity of oil in the olive fruit, keeps increasing until the very last moment it is harvested from the tree. So instead of picking the olives in November or December when they are ripe, we will get more oil, if we wait until February or March. The earlier the picking, the better the quality of the olive oil. If quality is aimed, the olives should be picked early.
Until the early 1900’s, after the olives were picked, they were transferred to the mill, where generally were placed on flat surfaces and turned over with a wooden shovel, once daily for about a week, to prevent molding. Then without any more delays were transferred to the mill to be crushed, or were placed in sacks where they were going to be kept for little longer and then would been shipped to an oil manufacturer, if the olive grower didn’t have the required press and crushing stone to making the oil himself.
The first pressing was made slowly and gently and gave the extra virgin olive oil. Then for the second pressing hot water was added and the pressing was made harder and gave the virgin olive oil.
The olive oil was placed in tin tanks and by sitting naturally for about a month, deposited its impurities on the bottom of the tanks. Then it was placed in cans or bottles for the market.
Another way for getting rid of the oil’s impurities, it was by filtering in tin barrels, with cotton batting at the bottom. This way it could been bottled and sold immediately after.
Finally in the remains of the second press, fermented olives were added (the ones that were fermented along the way), with plenty of hot water and pressed once more very hard. This time the pressing was done in a different press, so the bad quality and flavor of the oil, wouldn’t effect the better qualities. It was considered highly essential for the extraction of better grades of oil, to maintain perfect cleanliness.
When the pressing was over, the remains were dried and used for feeding the animals or used for fuel and etc.
Sieuve says that one hundred pounds of olives give thirty two pounds of oil.
Decandolle says the quantity of olive oil produced by the olive is fifty per cent of its weight.
Other writers say that the average proportion is twenty- five per cent.
This proportion varies, according to the variety of the olive. There are some varieties that give fifteen and even ten per cent. Another fact is the time of harvesting the olive. For quality pick early, for quantity pick late.