An essential oil
is a water-immiscible material produced by distillation
from some plant
material. The material (flowers, leaves, stems, or roots, depending on the plant) is put in an alembic over water
, and the volatile compounds, which require less vapor pressure
to evaporate with the presence of steam, distill into a receiving vessel. The upper portion is usually the oil, the lower being the hydrosol
. They are drained with two spigots.
Most oils are distilled in a single process. The exception is ylang-ylang, which takes 22 hours to complete distillation. It is distilled fractionally, producing several grades.
Many essential oils have medicinal properties and are used in aromatherapy. For instance, tea tree is a broad-spectrum antiseptic, and ylang-ylang relaxes the brain and the heart.