Through distillation, the plant material is placed upon a grid inside a still. Once the still is sealed, steam or water slowly breaks through the plant material. The materials rise upward through a connecting pipe that leads them into a condenser. The condenser cools them back into liquid form. Since water and oil do not mix, the essential oil will be found on the surface of the water where it is siphoned off.
A more modern method of extraction specifically for citrus or flowers involves prodding and pricking actions to release the essential oil. The fruit is placed in a container with spikes that puncture the peel, releasing the oil that is collected in a container below. Once in the container, a machine is used to spin in a centrifuge to separate the essential oils from the fruit juice.
CO2 gas has the unique ability to reach a supercritical state (neither completely gas or liquid), at a relatively low temperature and pressure. First, the CO2 gas is heated and pressurized to a supercritical state and then added to the plant material. The resulting mixture is filtered to remove any leftover plant material and the pressure and heat are reduced. This causes the CO2 to return to its gaseous state, evaporate out of the oil, leaving a pure essential oil behind.