Many of the most common essential oils are steam distilled. It is the same process you see in the movies of people making moonshine. Sometimes the big copper coil and all are used. The plant matter, which may consist of flowers, roots, leaves, and more, is placed in the distillation apparatus with water (also known as an alembic vessel or simply a “still”) where the water and plant matter are heated. The plant material releases aromatic material as the steam forces the essential oils in the plants to burst open and escape, evaporating into the steam. The temperature of the steam is carefully controlled - just enough to force the plant material to let go of the essential oil, yet not so hot it would burn the plant material or the essential oil.
The steam containing the essential oils passes through a cooling chamber, causing condensation. The collecting tube is often coiled and is housed within an outer container through which the cool water flows. This allows the fluid to condense and drip into the collector. In the collector, the essential oil separates from the hydrosol or aqueous portion. Distillation may take anywhere from a couple of hours to nearly twenty hours, depending on the plant matter being distilled.
This is where hydrosols come from. They are literally the water used in the distillation process.
This is also known as cold pressing. Most citrus peel oils are expressed mechanically, or cold pressed (similar to olive oil extraction). Due to the relatively large quantities of oil in citrus peel and low cost to grow and harvest raw materials, citrus-fruit oils are cheaper than most other essential oils. You can actually squeeze essential oil out when you peel an orange or a lemon. No heat source is needed for this extraction method, which is why it is called “cold pressing.” While today large machines do all the pressing, in early times the rinds were hand squeezed onto sponges in order to collect the precious oils.
This is an older method not frequently used today. In cold enfleurage, a large framed plate of glass, called a chassis, smeared with a layer of animal fat (usually lard or tallow) is allowed to set. Most oils collected with this method are flowers. Petals or whole flowers placed on the fat diffuse their scent into the fat over the course of 1-3 days. The spent flowers are replaced with fresh ones until the fat has reached a desired degree of fragrance. This procedure was developed in southern France in the 19th century for the production of high-grade concentrates. In hot enfleurage, solid fats are heated and botanical matter stirred into the fat. Spent botanicals are repeatedly strained from the fat and replaced with fresh material until the fat is saturated with fragrance. This method is the oldest known procedure for preserving plant fragrance substances. Jasmine was commonly a popular flower that went through the enfleurage process.
Solvent extracted is almost exactly how it sounds. This is how absolutes are made. Flowers are covered with a solvent (hexane, for example) which extracts the essential oil from the flowers/plants. Solvent extraction does not always have to mean the solvent was unnatural. Sometimes solid oils, fats, or carbon dioxide are used (think high-tech-enfleurage). The primary reason for using this method is for flowers that are too delicate to be steam distilled. Jasmine Absolute is made using the solvent extraction method.
There have been many times over the years that I have encountered people that tell me they make their own essential oils. I immediately ask them if they own a farm, because distilling essential oils takes an enormous amount of plant matter. When the answer is no, I ask them about the process – only to find that they are actually making infused oils. I can remember back many years ago when I tried this and thought I was making my own essential oils. I took the peel of several oranges and packed a canning jar full then poured sweet almond oil over the peels, capped it, and allowed it to sit for two weeks. The result was sweet, orange-smelling oil. However, when I purchased my first essential oil book some weeks later I discovered that my jar of citrusy oil was far from being an actual essential oil. This is how we learn: experimentation and research.
Infused oils involve taking plants and allowing them to soak in carrier oil, usually a liquid vegetable oil, for an extended period, giving the plant time to release its properties into the base. Most of the time, the method is to leave the jar sitting in the sunlight (such as a windowsill) so that the carrier oil will be heated gently and naturally, which encourages the plant matter to release more of its precious oils.
While it may not be an essential oil, this is still an excellent way to make your own herbal-based massage oils. The key to success is absolutely cleanliness. The jars should first be sterilized (a dishwasher will do) then thoroughly dried. There should be absolutely no water, not even a drop, left inside your glass jar because water will be the foundation for the growth of bacteria.
If using fresh herbs from your garden, wash them to get rid of any dirt or bugs, and allow them to dry completely. I don’t mean turning them into a dried herb – just the process of getting all water off of the plant. If this means putting your project off until the next day, so be it. Knowing this, you may want to cut your plants and rinse them the day before you plan your infusion project. You can speed up the process by blotting the plants with paper towels.
When your plants/herbs are completely dry, you want to bruise them – meaning, you’re going to pinch or rub the leaves slightly to help bring some of the essential oils out. Some people go a step further and chop the herbs. Then, pack your jar at least half-way with the herb (almost all the way to the top is best) and cover with your carrier oil. Fill the jar with oil as far as you can. Leaving a lot of airspace at the top gives more chance for mold to occur.
Olive oil is a popular choice but many people also choose: canola oil, sunflower oil, safflower oil, or even common vegetable oil. You may also use more exotic oils, such as sweet almond or grapeseed oil. Just be sure not to choose oils that become rancid easily, especially if you are going to place your infusion in a sunny windowsill.
Cap the jar tightly and gently shake or swirl the contents each day.
I never use the sunlight method when I infuse oils. I prefer to place the jars in a dark, room-temperature spot for about two weeks. There are many who feel that the addition of sunlight does more harm than good to the integrity of your base oil. Furthermore, the sunlight and heat can cause condensation in the jar. Usually, the darkroom method will give you a lighter colored finished product.
After the herbs have steeped for a few weeks, strain the contents through cheesecloth several times so that no plant matter remains in the carrier oil. Bottle and store away from light. The product should be good for at least six months, although I have seen some infused oils last for a couple of years. At this point, you may also choose to add vitamin E to the oil by breaking open several capsules and spilling their contents into your infused oil, which will help with rancidity. If you have chosen oils that tend to go rancid more quickly than others do, you may choose to store your finished product in the refrigerator.