Criteria of a good distillation

Steam distillation is a delicate process demanding experiment and a constant monitoring. To obtain a first quality essential oil, the following criteria must be observed:

Alambic

The Alambic is ideally made of stainless steel, the most inert material as copper and iron can form oxides

Low-pressure

The distillation must be conducted under very low pressure, between 0,05 and 0,10 Bar as over oxidation are possible at high pressure. For example, the colour of essential oil of flowered thymus vulgaris varies from pale red to red-brown by increasing the pressure. The pyrogénation of woods with barks, resulting from a steam distillation at high pressure and high temperature produce essential oils soiled with carcinogenic tar.

Completed distillation

The duration of the whole distillation is of great importance. Long and prolonged, it will allow collecting the “totum” of the aromatic molecules i.e. base and topping notes of the essential oils.
For example: ¾ of the essential oil of thymus vulgaris are extracted during the thirty first minutes, but sixty to eighty additional minutes are required to extract the phenols. The producers are paid by kilogram of essential oil. That is the reason a lot of them distil under high pressure and stop the distillation after the 25 to 30 profitable minutes. Those essential oils are frequently rectified i.e. re-distilled to cleanse it from undesirable components and to concentrate the most volatile molecules. This process produces fade essential oils with a less fine smell and more side effects.
Thus a rectified essential oil of eucalyptus can contain up to 80% eucalyptol, but is more irritant for the bronchial tubes then a complete essential oil of eucalyptus containing only 60% eucalyptol.

Spring water

The use of spring water, poorly calcareous is always preferable to avoid chemical descaling agent

Storage and preserving

After distillation, the essential oils must be filtered and then stocked in inalterable hermetic tanks stored in a fresh cellar. They must only be bottled in brown or blue opaque glass bottles to ensure their conservation safe from the light and oxygen.