Most essential oils are made by steam distillation: steam is passed through plant material, it carries the plant’s aromatic compounds out with it, and when the steam cools the oil separates from the water and is collected. Citrus oils are the main exception. They are cold pressed from the fruit peel. Delicate flowers like jasmine, which can’t survive distillation, are solvent extracted into a related product called an absolute, and a growing number of oils are now made with supercritical CO2 extraction.

Below is how each method works, which oils it’s used for, and what happens to the plant before and after extraction.

The 5 Main Ways Essential Oils Are Made

Method	How it works	Used for	Examples
Steam distillation	Steam passes through plant material and carries the oil out	Most leaves, herbs, flowers, wood, roots, resins	Lavender, peppermint, eucalyptus, tea tree
Water (hydro) distillation	Plant material is boiled directly in water	Flowers that clump under steam	Rose otto, neroli
Cold pressing (expression)	Peels are mechanically pressed, no heat	Citrus fruit	Lemon, orange, bergamot, grapefruit
Solvent extraction	A solvent dissolves the aromatics, then is removed	Fragile, low-yield flowers	Jasmine, tuberose, rose absolute
Supercritical CO2 extraction	Pressurized CO2 acts as a solvent, then evaporates	Spices, roots, resins, some flowers	Ginger, frankincense, turmeric

1. Steam Distillation

Steam distillation is the standard method and produces the large majority of essential oils on the market.

Here’s how it works:

1. Plant material is packed into a still.
2. Steam is pushed up through it from below. The heat and moisture rupture the plant’s oil glands and release the volatile aromatic compounds.
3. Those compounds travel with the steam into a condenser, a coil cooled by cold water.
4. The steam turns back into liquid, and the mixture drips into a separator (often called a Florentine flask).
5. Oil and water don’t mix, so they separate into layers. Most essential oils are lighter than water and float on top, though a few, like clove and cinnamon, are heavier and sink.
6. The oil is drawn off. The water left behind is the hydrosol (more on that below).

The skill is in the control. Too much heat or pressure can damage delicate compounds and change the aroma; too little leaves oil behind in the plant. Distillation time matters too. Some compounds come over early and others only after hours, so a shortened run can produce an oil that smells incomplete.

2. Water Distillation

Water distillation (also called hydrodistillation) is the oldest form of distillation. Instead of steam passing through the plant, the plant material is submerged in water and the whole mixture is boiled.

It’s used mainly for flowers like rose petals and orange blossoms, which tend to clump together into a dense mass under steam, so the steam can’t pass through evenly. Floating in water, they stay loose. The condensing and separating steps are the same as in steam distillation.

The water acts as a buffer against direct heat, which can give a softer aroma, but the still has to be watched carefully so the plant material doesn’t scorch.

3. Cold Pressing (Expression)

Citrus oils come from tiny oil sacs in the outer peel of the fruit, and they’re extracted mechanically rather than with heat:

1. The whole fruit or its peel is pressed, rasped, or punctured to burst the oil sacs.
2. The released oil is rinsed off with water, giving a mixture of oil, water, juice, and peel solids.
3. A centrifuge spins the mixture to separate the oil.

Because no heat is used, cold-pressed oils keep the bright, fresh smell of the fruit. The trade-off is shelf life: citrus oils oxidize faster than most distilled oils, so they’re best used within a year or two and stored cool and dark. Cold-pressed citrus oils, bergamot especially, can also make skin more sensitive to sunlight. Some citrus oils are steam distilled instead to remove those compounds, which changes the scent.

4. Solvent Extraction (Absolutes)

Some flowers, like jasmine and tuberose, are too fragile for heat or contain too little oil for distillation to be practical. For these, producers use solvent extraction:

1. Flowers are washed with a solvent such as hexane, which dissolves the aromatic compounds along with natural waxes and pigments.
2. The solvent is evaporated off, leaving a waxy, fragrant solid called a concrete.
3. The concrete is washed with alcohol, which pulls out the aromatic part and leaves the waxes behind.
4. The alcohol is removed, leaving the absolute.

Absolutes are richer and closer to the smell of the living flower than distilled oils, which is why perfumers prize them. But strictly speaking they’re not essential oils. They’re a separate category, they can contain trace solvent residue, and aromatherapists often treat them differently because of that.

5. Supercritical CO2 Extraction

CO2 extraction is the newest method in wide use. Carbon dioxide is put under high pressure and slightly warmed until it becomes “supercritical,” a state where it penetrates plant material like a gas but dissolves oils like a liquid. Producers typically run it at around 35–60°C (95–140°F), far below the boiling temperatures of distillation.

The CO2 flows through the plant material, picks up the aromatic compounds, and then moves into a lower-pressure chamber where it turns back into a gas and escapes, leaving the extract behind. The CO2 is recaptured and reused, and no solvent residue remains.

Because it uses less heat, CO2 extraction can capture compounds that distillation damages or misses. That’s why a CO2 extract of ginger or frankincense often smells closer to the raw plant than the distilled oil does. The downside is cost: the equipment is expensive, and so are the extracts.

A Historical Method: Enfleurage

Before modern solvents, perfumers in Grasse, France, captured jasmine and tuberose through enfleurage. Fresh petals were laid on glass plates coated with odorless purified fat, which slowly absorbed their scent. Petals were replaced daily for weeks, and the saturated fat (called a pomade) was then washed with alcohol to pull out the fragrance. It’s extremely labor intensive and almost never used commercially today, but it’s where many modern techniques came from.

What Happens Before Extraction

The extraction method gets most of the attention, but a lot of what ends up in the bottle is decided earlier.

The plant part. Essential oils come from different parts depending on the species: flowers (lavender, rose), leaves (eucalyptus, peppermint), bark (cinnamon), roots (vetiver, ginger), wood (sandalwood, cedarwood), resin (frankincense, myrrh), seeds (cardamom), and fruit peel (all the citrus oils). The part used affects both how much oil you get and how it smells.

Growing conditions. Soil, altitude, rainfall, and temperature change the chemistry of the oil. The same lavender species grown at high altitude and at low altitude can smell noticeably different, which is why many suppliers list the country of origin.

Harvest timing. Plants don’t hold the same amount of aromatic compounds all season. Lavender is typically harvested when most of its flowers have opened, many herbs are cut just before flowering, and roses are picked early in the morning, before the day’s heat drives off their scent. Roots like vetiver are dug up only after the plant has matured for a year or more.

Preparation. Some plants are distilled fresh within hours of harvest, while others (like some roots and seeds) are dried first. The material is often chopped or crushed so steam can reach more of the oil glands.

What Happens After Extraction

Separating oil from hydrosol. Distillation produces far more water than oil. That water, called a hydrosol or floral water, keeps a small amount of dissolved oil plus water-soluble plant compounds. Rose water and lavender water are both hydrosols, and they’re sold as products in their own right for skincare and cooking.

Resting and filtering. Freshly distilled oil can smell harsh or “stilly” and may be slightly cloudy. Many producers let it rest for weeks so the aroma settles, then filter out any remaining water or plant particles.

Testing. Reputable suppliers test each batch with gas chromatography–mass spectrometry (GC-MS), which breaks the oil down into its chemical components. This confirms the oil matches what it should be for its species and catches dilution or adulteration with cheaper oils or synthetics. Many suppliers will share these reports if you ask.

Bottling. Essential oils go into dark amber or cobalt glass because light speeds up their breakdown. Plastic is avoided because concentrated oils can degrade it. Heat, light, and air remain the main threats after bottling, so a tightly sealed bottle kept somewhere cool will last much longer.

Why Some Essential Oils Cost So Much More Than Others

Price mostly comes down to yield: how much plant material it takes to make a given amount of oil.

• Lavender is relatively efficient. True lavender yields about 1.2% oil from dried flower stems, or roughly 80 kg of dried stems for 1 kg of oil.
• Rose otto is the classic extreme. Rose petals yield only around 0.02–0.03% oil, which works out to roughly 3,500–5,000 kg of petals for a single kilogram of oil. The petals also have to be hand-picked in early morning during a short bloom season.
• Citrus oils are among the cheapest because the peel holds a lot of oil and the fruit is already being grown and processed for juice.

So when rose otto costs many times more than lemon oil, that’s not just branding. It reflects how much land, labor, and plant material went into it. The flip side is that a suspiciously cheap rose or sandalwood oil is a red flag for dilution or adulteration.

Frequently Asked Questions

Can you make essential oils at home?

You can, with a small home distillation kit (copper and glass stills are sold for hobbyists), but expect very little oil. Because yields are so low, a home batch of herbs often produces only a few milliliters of oil along with a lot of hydrosol. Infusing herbs in a carrier oil like olive or jojoba is much easier, but that makes an infused oil, not an essential oil.

Are absolutes and CO2 extracts the same as essential oils?

Not technically. In the strict definition, an essential oil is made by distillation or, for citrus, cold pressing. Absolutes (solvent extracted) and CO2 extracts are related aromatic products with different chemical profiles, and they’re usually labeled as such.

What’s the difference between an essential oil and a hydrosol?

An essential oil is the concentrated, water-insoluble aromatic fraction of the plant. A hydrosol is the water left over from distillation. It carries only a trace of the oil, so it’s much gentler and can generally be used directly on skin, while essential oils should be diluted.

Which extraction method makes the best essential oil?

There isn’t a single best method. Each suits different plants. Steam distillation is right for lavender and peppermint, cold pressing captures citrus best, and solvent or CO2 extraction works for plants that heat would damage. Quality depends more on the plant material, the care of the producer, and testing than on which method was used.

How long do essential oils last?

Most distilled oils last two to three years if stored well. Citrus oils are shorter-lived, around one to two years, because they oxidize faster. Thick oils from woods and resins, such as sandalwood, patchouli, and vetiver, can last many years and often improve with age.