Traditional olive oil is made by crushing olives into a paste with stone mills, pressing that paste through woven mats to squeeze out the liquid, and then letting the oil naturally separate from the water. The process has remained remarkably consistent for thousands of years, dating back to the early Bronze Age in the eastern Mediterranean. While modern producers use steel machinery and centrifuges, the traditional method relies on gravity, stone, and patience.
Harvesting the Olives
The process starts in the grove. Traditionally, olives are picked by hand or knocked from branches with long wooden poles onto nets spread beneath the trees. Hand picking is slow and accounts for 40 to 50 percent of total production costs, but it produces the least fruit damage. Bruised olives begin to oxidize and ferment almost immediately, which raises acidity and degrades flavor. For this reason, hand picking remains the standard in small groves across Italy, Greece, and other Mediterranean countries where premium oil is the goal.
Timing matters as much as technique. Olives picked earlier in the season, when they’re still green or just turning color, yield oil with sharper, more peppery flavor and lower acidity. Fully ripe black olives produce milder, butterier oil but are more fragile and prone to bruising. Regardless of ripeness, the olives need to reach the mill quickly. Processing within hours of harvest limits oxidation and bacterial activity, keeping acidity low and flavor clean. Delays of even a day or two can noticeably degrade the final product.
Washing and Preparing the Fruit
Once at the mill, the first step is washing. Olives arrive with leaves, twigs, and soil clinging to them. Soil in particular can create an unpleasant “earth taste” in the finished oil, so a thorough rinse in cold water removes surface contaminants before crushing begins.
In some ancient traditions, freshly collected olives were placed in a large tub and sprinkled with salt before milling. The salt generated mild heat, induced sweating, and pushed the fruit toward a more advanced stage of ripeness. This made the olives softer and easier to crush, improving oil extraction. While not universal, this preparation step appears in historical records from the Levant, where olive oil production originated roughly 5,000 to 6,000 years ago.
Crushing With Stone Mills
The heart of traditional olive oil production is the stone mill. A large, heavy millstone (usually granite or volcanic rock) sits in a circular basin. As the stone rolls over the olives, it crushes both the fruit flesh and the pits into a thick, uniform paste. In older mills, a donkey or ox walked in circles to turn the stone. Later versions used a hand crank or water power.
Stone milling works slowly and gently compared to modern hammer mills or steel blades. The slow crushing releases oil from the olive cells without generating excessive heat or the harsh shearing action of industrial equipment. This matters because heat degrades the delicate flavor compounds and antioxidants in the oil. To qualify as “cold pressed” or extra virgin under modern regulations, the paste temperature cannot exceed 27°C (about 81°F) during extraction. Top producers aim for a few degrees below that threshold, since even small temperature differences affect the final product. Traditional stone mills naturally stay within this range because they simply don’t generate much friction.
Kneading the Paste
After crushing, the olive paste is collected and kneaded, a step called malaxation. This involves slowly stirring the paste for 20 to 40 minutes so that the tiny oil droplets scattered throughout the pulp merge into larger drops. Without this step, much of the oil stays trapped in the paste and never makes it into the press.
Kneading was traditionally done by hand or with simple wooden paddles. The key is to keep the process gentle and the temperature low. Over-mixing or working the paste too aggressively introduces air, which accelerates oxidation. The goal is just enough mixing to let the oil pool together without compromising freshness.
Pressing Through Fiber Mats
This is the step most people picture when they think of traditional olive oil. The kneaded paste is spread onto round, flat mats called fiscoli. These mats were historically woven from hemp, though rush, palm fronds, and willow were also common depending on the region. The loaded mats are stacked on top of one another on a central pole, forming a tall column.
Pressure is then applied from above. The earliest presses used a heavy stone weight placed on top of the stack. Later innovations introduced the lever press and then the screw press, which allowed more controlled, gradual pressure. As the stack compresses, liquid streams out from the edges of the mats and flows down into a collection basin or pit below. This liquid is a mixture of olive oil and the fruit’s natural water content (historically called amurca, the watery lees).
A single pressing doesn’t extract all the oil. Producers often restacked and pressed the mats a second or third time to capture remaining oil, though each subsequent pressing yielded less and produced lower quality. The term “first cold press” originally referred to the oil from this initial pressing, before anyone reapplied pressure or added hot water to coax more oil from the pulp.
Separating Oil From Water
The liquid that comes off the press is not pure oil. It contains a significant amount of vegetable water plus fine particles of olive pulp. Traditionally, this mixture was poured into large settling containers, often made of terracotta or stone, and simply left alone.
Over several weeks or even months, gravity did the work. Solid particles and impurities sank to the bottom, while the lighter oil floated to the surface. Producers then carefully skimmed or ladled the clear oil from the top, a process called decantation. Some also poured the liquid through a spigot positioned at the right height on the container wall to draw off only the oil layer. For centuries, this natural settling was the primary separation method across the Mediterranean.
For extra clarity, the decanted oil could be filtered through cloth or cotton to remove any remaining fine sediment. Unfiltered oil retains more particles and has a cloudier appearance, which some people prefer for its fuller flavor, though it has a shorter shelf life.
Storing the Finished Oil
Once separated and filtered, the oil needs protection from its three enemies: air, light, and heat. Traditional producers stored oil in terracotta vessels, glass containers, or tin-lined tanks kept in cool, dark cellars. Ancient sources, including the Byzantine agricultural manual known as the Geoponica, recommended adding a small amount of salt and nitre (a mineral salt) when storing oil to help preserve it.
Proper storage is not optional. Exposure to light or warmth accelerates rancidity, and contact with air increases free fatty acids over time. This is why traditional Mediterranean oil cellars were built underground or into hillsides, maintaining naturally cool, stable temperatures year-round.
How Much Oil the Olives Actually Yield
Traditional extraction is not especially efficient. On average, it takes roughly 7 to 8 kilograms of olives to produce a single liter of oil, though this varies widely depending on the olive variety, ripeness, growing conditions, and how thoroughly the paste is pressed. A small farmer delivering 600 kilos of olives to a traditional mill might receive only about 80 liters of oil in return. Year-to-year variation is normal, and olive trees are naturally cyclical, producing heavier crops in alternating years.
This low yield is one reason genuine traditionally made olive oil carries a premium price. Between the labor-intensive hand harvest, the slow stone milling, and the weeks of patient decantation, every liter represents a considerable investment of time and physical effort. It is also why the process has survived: producers who use it consistently argue that the gentler handling preserves flavors and nutrients that faster, industrial methods sacrifice for volume.