Building a Lever-and-Weight Olive Press — Mechanical Extraction

Before pressing, the olives must be crushed to a paste (including the pits) to rupture the oil-containing cells. Use a stone olive mill (trapetum) — a large stone basin with a rounded stone roller that crushes olives as it is rotated. Alternatively, crush the olives in a stone mortar with a heavy pestle, or tread them underfoot on a clean stone surface. The paste should be uniform, with no whole olives remaining. Including the crushed pits is important — the hard pit fragments act as channels that help oil drain through the paste during pressing. Allow the paste to rest for 30-60 minutes before pressing to let oil begin separating.

The lever press consists of a heavy beam anchored at one end and free to pivot at the other. Fix the thick end of the beam into a slot carved in a stone wall or between two upright stone pillars (orthostats) — this is the fulcrum. The beam must be rigidly held at this point so it can only move up and down like a see-saw. The free end extends 3-5 metres outward. Beneath the beam, near the anchor point, construct a flat stone pressing platform with a channel around its perimeter to collect the expressed oil and direct it into a stone basin. This is a class 2 lever — the load (olive paste) is between the fulcrum and the effort (weights).

Spread the crushed olive paste onto flat, round woven rush baskets (called frails or fiscoli), building a stack 5-10 baskets high beneath the beam. Each basket holds 5-10 kg of paste, spread 3-5 cm thick. The woven structure allows oil to seep through the rush fibers while retaining the solid pomace. Place flat wooden or stone discs between every 2-3 baskets to distribute pressure evenly through the stack. Position the stack directly beneath the beam, centred on the pressing platform. The collection channel around the platform catches all expressed oil and drains it into the stone basin.

Hang heavy stone weights from the free end of the beam using ropes. The lever effect multiplies the force of the weights — a 3-metre beam with weights at the end generates roughly 3 times the weight force at the pressing point. Add weights gradually to increase pressure slowly. Sudden pressure causes the paste to squeeze out of the baskets rather than releasing oil. Oil begins flowing within minutes of initial pressure application. Continue adding weights over several hours. The first pressing (cold-pressed) produces the finest quality oil — pale green, fragrant, and lowest in acidity. After the first pressing, the pomace can be remixed with hot water and pressed again for a lower-quality second pressing.

The liquid collected in the basin is a mixture of olive oil and water (vegetation water from the fruit). Because oil is less dense than water (olive oil density is approximately 0.91 g/cm3), it floats naturally to the surface. Allow the mixture to settle in a deep stone or clay vessel for several hours. Skim the oil layer off the top using a flat ladle or shell, or decant it by siphoning. Transfer the oil through progressively smaller settling vessels to remove residual water and sediment — three stages of settling was standard in ancient oil production. Well-settled olive oil stores for up to two years in sealed clay amphorae kept in a cool, dark place. The ancient Mediterranean economy ran on olive oil — it was used for cooking, lighting, bathing, religious ritual, medicine, and as the base for perfumes and cosmetics.