How did hydraulic presses improve oil extraction from seeds?

The development of the hydraulic press in the early 19th century significantly improved oil extraction from seeds by enabling the application of much higher pressures compared to earlier methods, such as the wedge or stamper presses.1

By utilizing these increased pressures, the hydraulic press was able to extract a considerably higher yield of oil from the seed material. In these systems, ground seed material was typically confined in cloths or, in closed-type presses, within strong perforated steel cages. These configurations allowed for pressures to reach approximately 400 kilograms per square centimeter or more, effectively reducing the oil content remaining in the residual cake to an average of about 5 percent.1

While the hydraulic press represented a major advancement over its predecessors, it has since been largely replaced in modern operations by the continuous screw press, which offers greater capacity, requires less labor, and can achieve even higher pressures to further minimize residual oil.21