The Extraction of Essential Oils by Distillation and Expression

Photo of a Simple Homemade Still

For anyone who studies essential oils, distillation is probably the most familiar method of extracting essential oils from plant material; however, not all essential oils can be steam distilled. Most citrus oils, for example, are expressed. So what does 'distilled' and 'expressed' mean? And why are there different methods of extracting essential oils?

Essential oils can be extracted in the following ways:

- Distillation - the most common method of extracting essential oils and a method which has been used for centuries essentially. Plant matter which is steam distilled is in placed in a still, heated and the essential oils (the 'aroma' molecules of the plant) evaporate into the steam. The molecules are then carried along a pipe and when they start to cool (as the pipe passes through a cold water vat) the molecules form into liquid - the essential oils. The essential oils can be separated from the water, as the essential molecules either "sink or float' on the water.


Distillation is used to extract essential oils from the sacs stored in the leaves, roots, seeds and flowers of plants. Aromatherapy and Botany explains more of the storage of essential oils by plants. Some plants have no difficulty producing a large quantity of essential oil in one batch, others are extremely difficult to extract from with minute quantities of essential oil produced in a single batch.

- Expression - citrus fruits are usually expressed to extract essential oils. Essential oils are located in the rind of the fruit and need to be 'squeezed' out - a bit like when you peel the orange and the juice is 'squeezed' out of the fruit, except it is the rind which is expressed in the case of the majority of the citrus essential oils. The problem with expressing pure essential oils from citrus oils is that, in today's world, many fruit trees are chemically sprayed, 'contaminating' the rind of many citrus fruits. For this reason, many aromatherapists prefer to use organic or naturally grown fruits for essential oils (although these terms can be 'open to interpretation' sometimes too!)

Newer methods of extracting essential oils include Carbon Dioxide Extraction (CO 2 essential oils) and Perculation which is coming up next...

Do you have any comments to add on my post on the extraction of essential oils? Add you comments below if you do!