Distillation
Historical Distillation of Plants, Oils and Waters
Historical texts vary in their accounts of the types of distillation practiced in the past, but one fact remains; distillation of plants has been around for a very long time, albeit not always in the form that we are familiar with today.
Distillation, in its crudest form, is defined by Encyclopedia Britannica as a, “…process involving the conversion of a liquid into vapour that is subsequently condensed back to liquid form.”1 However, as any experienced distiller will tell you, distillation is not only a scientific process but a true art as well.
Plants are placed in the still, through either water or steam distillation (see The Process of Distillation below) and transformed from plant to steam to liquid through a complex system of managing plant matter, heat, and water. The end result produces either an essential oil or hydrosol.
We may never know the exact process of how early civilizations turned plants into oils and hydrosols, but an interesting paper on the Early History of Distillation by T. Fairley, F.R.S.E., F.I.C, from 1906 discusses various methods of distillation practiced by ancient people of India, Arabia, China, Phoenicia, Greece, and Rome.2 Indeed, Ann Harman in her book Harvest to Hydrosol states that: “The oldest [alembic] still that has been discovered, to date, is almost 4000 years old.”3 The still which she is talking about was found by Dr. Maria Rosaria Belgiorno at Pyrgos in 2005.
Most historical texts agree that the ancient Egyptians were using plants as oils for perfumery and medicinal practice, as well as religious purposes. Scent was revered by the ancient Egyptians as a key to everlasting life. Aromatic oils and plants were used in all aspects of daily life.4 The ancient Greeks and Romans then learned techniques and use of plants and oils from the Egyptians. However, it was a physician from Persia by the name of Avicenna (980 A.D. – 1037 A.D.) who made a significant contribution to how plants are distilled today; the addition of the refrigerated coil into the still.5
Methods of Extraction
The two most common forms of distillation of both essential oils and hydrosol are steam distillation and water (hydro) distillation. The primary difference between these methods is that with water distillation the plant material is based within the water and with steam distillation the plant material is based above the water. Sometimes a distiller may perform a combo-distillation which is essentially a combination of both methods of extraction.
The distillation process for essential oils and hydrosols is broken down as follows:
- Plant material (for example leaves, flowers, twigs, or seeds) is placed in a vat (either in the water itself of on a screen in which steam passes through).
- Heat is applied underneath the vat.
- The essential oil molecules from the plant material “escape from the plant” and evaporate into steam which is forced along a pipe.
- The pipe passes through a cold-water vat and, as the steam cools, the essential oil molecules turn into liquid –the essential oil. Essential oil molecules will either “sink” or “float” on the water, which means that they can easily be separated from the water to be used as an essential oil. Conversely, the water can be drained off to be used as a hydrosol.
