Steam Steam generated in an external boiler is passed into the bottom of the retort. The Retort holds the plant material, in a commercial still, several tonnes of material per batch.
Steam passes up through the perforated floor and vapourises the volatile oil.
The vapour mixture passes into the top of the condenser. Here it passes down a bundle of tubes cooled in a jacket of water flowing in the opposite direction. The oil and water mixture flows into the separator where the generally lighter oil rises to the top. The oil can be drawn off from time to time as the layer builds. The water, which contains traces of slightly soluble fractions of the oil is drawn off continuously from the bottom of the separator.