INTRODUCTION

There are many ways to extract essential oils from plants. Essential oils are highly concentrated extracts and should not be confused with infused oils, tinctures and infusions which draw only the volatile components from the plant. Essential oils are produced by steam distillation, cold pressing, solvent extraction or hyperbaric extraction. Each extraction method has strengths and weaknesses and the character and quality of the oil can vary depending upon the method used. These methods of extraction are often unsuitable for home use because of the large amounts of plant material needed to extract a small amount of essential oil.

STEAM DISTILLATION

This is the most common form of extraction which makes use of the ability of stem and pressure to draw out components from the plant material. The plant material is placed on screens and steam, often heated at high pressures is passed thorough the material. This has the effect of drawing out the volatile components. This oil bearing steam is then condensed to precipitate out as a mixture of volatile components and distilled water. The mixture is collected and the distilled water, being heavier sinks to the bottom leaving the essential oils at the surface. The essential oil can then be drawn off.

Variations of steam distillation use low heat and take a long period to distill a batch of oil. These methods can result in a better quality oil as the larger molecules can be drawn out of the plant material. High temperature methods, favored for modern mass production can produce essential oils more efficiently lowering the cost but some of the bouquet can be lost with this method.

COLD PRESSING

This method is widely used in the production of oils from Citrus rinds such as Lemon, orange, grapefruit, tangerine, bergamot or mandarin. The rinds are chopped, then ground, then pressed to force the essential oil components found in the skin. This cold pressing produces a mixture of water and essential oils. This mixture is then allowed to settle and the essential oils drawn off.

SOLVENT EXTRACTION

This method is suited to light floral oils. A solvent (such as Hexane or ether) is used to dissolve the volatile components. The solvents are then evaporated to leave a thick residue known as an 'Concrete' this can be dissolved in alcohol and the alcohol drawn off to leave an essential oil often known as an 'absolute'. This method is preferred by perfumers who maintain that the essential character of the floral bouquet is retained by this method. For Aromatherapy use oils produced in this way have the disadvantage that some of the solvent will remain within the oil. Oils produced in this way should not be used for internal treatments.

HYPERBARIC PRODUCTION

This method makes use of high pressures (as much as 22 atmospheres) and the presence of pure carbon dioxide gas. The high pressure causes the CO2 gas to liquefy. In this form the gas has the ability to forma solution with the volatile components of the plant material. The liquid gas is then drained off and de-pressurized thus leaving behind a deposit of pure essential oil. The cost of the equipment needed for this process makes it costly but it is especially suited for the extraction of many of the lighter oils such as jasmine.

PRODUCING INFUSION

This method produces an infusion rather than an essential oil but it is suitable for home use. The recipe given is for dried herbs. Fresh herbs should be left for six to eight hours to allow the water content to drop. If using fresh materials such as flowers the amount needed may vary.

Measure the herbs and oil and mix the oil to the herbs in a stainless steel bowl, about 15gm of dried or 30gm of fresh herbs. Heat over water bath (a saucepan 1/4 filled with water) also known as a double boiler, this should be simmering. The bowl should not be sitting on the bottom of the pot but is floating in the water. Keep the lid on the oil. Stir occasionally and simmer for 30 minutes. The oil should not be allowed to overheat. It should not smoke or bubble. It can burn easily and will develop an acrid smell if it overheats. Strain through four layers of butter muslin or some other very fine non-metal strainer. Strain twice if necessary as it is important to remove all herbs to prevent the oil spoiling

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