The oil is contained in excretion containers between the cuticle (wax layer) and the cell membrane of the flowers. The flowers with stems are broken down with hot water and steam: the essential oil escapes from the oil containers of the flowers and is dissolved with the steam. If the water/oil mixture is cooled down, phase separation occurs due to the different densities. The lavender oil can therefore be easily decanted and bottled.
Due to the thermal energy supplied in the process, water-soluble substances are also extracted. These substances and a low limiting concentration of essential oils remain in the water and produce the so called hydrolate or flower water. This water gets returned to the process.
The essential oil is not as intense in fragrance as of the real lavender. It contains less esters like linaly acetate, but more monoterpenes (alcohols, ketones) like linalool, 1-8 cineol and camphor. With lavender oil, it is above all the ester content that is decisive for the quality: the higher, the better.