Essential Oils and Steam distillation

What is “Essential Oil”

When I think about this, I sigh – and stare out the window at the birds on the tree, essential oils, such an enigma.

Wikipedia describes them as “a concentrated hydrophobic liquid containing volatile aroma compounds from plants”,

a pragmatic answer – a concentrated substance that is repelled from a mass of water (hydrophobic) that has smell or

odour (aroma compounds). Apparently they are “essential” as well!

When I’m out walking, I see and feel a plant, reach out and pick a leaf or flower, crush it in my palms, cup my hands,

cover my mouth and nose and deeply inhale. The plant and I begin our conversation. We use the silent language of

aroma and sensation. How I wish I could translate all that into academic words that make sense, but I have learnt to

trust that the plant shares information with each aromatic conversation conducted with mindful body awareness

and sensitivity. So maybe it is the soul part of the nature of plants that can speak. Aroma is certainly a powerful

conduit of subtle change, response and reaction. Essential oils are aroma.

To be able to steam distil plants I have found or grown myself has been a profound experience. Even though the

process is quite simple, you become part of a magical alchemy of transformation. The energy of steam changes the

chemistry of a plant so that its constituents are released into liquefied steam. That in itself is enough, however then,

that liquid releases millions of tiny bubbles of aromatic essential oil. It is lighter than water so floats to the surface

and here gathers the volatile aromatics – the essential soul of the plant.

The Process of Steam Distillation

Steam distillation is mostly used to produce essential oils. The plant material is subjected to steam under pressure. It

does not come into contact with the boiling water. Water boils at 100 0 C

, steam has a higher temperature than

boiling water; a steam burn is worse than a boiling water burn.

Distilling for Essential Oil by Steam Distillation

I’m going to use Rosemary again as I’m taking up where I left off in

my last article in the Avena Winter Edition - Hydrosols and Hydro-

distillation. I hope I can illustrate the difference between the two

distillation methods and the difference in the hydrosols produced.

I use a Copper Alembic Column Still for steam distillation, the only difference between this and the one I used for

hydro-distillation – the Traditional Alembic Pot Still, is it has a Column that sits on the pot with a sieve plate at the

bottom. The herb is placed in the column; the column is placed on top of the pot of boiling water. The sieve plate

keeps the herb material above the water so only steam comes into contact with it.

Traditional Copper Alembic Column and Parts

I have my Column Still set up in a sheltered spot in the

garden. I have already cleaned it by distilling rye flour

slurry. To do this I mix 450g of Rye Flour in 4 L of water

and pour into the pot. I assemble the whole still and

heat the rye flour mix until it boils. It becomes frothy

and seeps out the joins. Once it comes out of the

condenser bucket as distillate, I turn the heat off.

When the Still is cool enough to handle, I dismantle it

and scour it with Eco Cream Cleanser (it contains a

citrus oil that cleans the copper). I rinse and dry it

thoroughly, leaving it in the sun to finish the drying

process. Before I start a new distillation I always distil

hot water to check the distillate is tasteless, odourless

and clear. I know I have a clean still.

The pot is 2/3 filled with water and placed on a gas

ring to bring the water to the boil. It’s important to

have everything at hand for a distillation. I have my

water pump on keeping a steady flow of cold water

running through the condenser bucket, my sterile

beakers and oil separators are ready to collect the

distillate. I have a bowl of rye flour paste to seal the

joins in my still so I don’t lose precious steam.

And of course I have harvested and prepared my herb. The leaves and flowers

have been stripped from the stems of the Rosemary and sit fragrantly waiting.

It is the same harvest I used for the hydro-distillation

I place 5 good handfuls of Rosemary into the column. When the water in the

pot is boiling, I carefully remove the onion dome and sit the column on the pot

making sure it square. I place the onion dome on the column, checking its

level. Because the Rosemary is cold I have a little time before the steam works

its way through.

I work quickly now. If I lose any steam, I will lose precious essential oil. I quickly

but carefully seal the join between the column and the pot and the column and

the onion dome with the rye flour paste. As the copper heats it bakes it dry and

seals the joins.

By the time I have done this, the onion dome is hot which means the steam has

spiralled up the column, the heat burst open the cells of the plant and the

volatile oils released and carried in the steam. The steam spirals in the onion

dome, any particles of dust of physical matter falls back. The steam flows down

the bird’s beak, through the connecting pipe and into the condenser coil.

Just as in the hydro distillation its vital to have a steady stream of cool water

runing aroung the condenser coil throughout the whole distillation. Its even

more important when distilling with steam, it’s a hotter faster distillation.

The water needs to be boiling vigorously to create a good body of steam

under pressure to burst the cellulose of the plants to release the essentail oil.

The distillate will flow faster than a hydro distillation. The essential oil will be

released in the first 200ml of distillate.

On a 10 L still I collect 500ml of Hydrosol. The oil has been expelled from

the mass of water and floats to the top. The hydrosol is not as milky as in

a hydro distillation and of course there is significantly more oil released.

The aroma is stronger, sharper and more intense. I check the pH.

Depending on my purpose I may continue distilling for hydrosol. There

will be very little oil in the next 500ml but often the hydrosol is still of a

good aroma, flavour and pH. As soon as the pH increases I stop the

distillation.

This is the best part! These are my oil separators. One is

500ml and other 60ml. They both sit in rings and are

clamped onto a retort stand. I use the larger separator

when distilling botanicals that will yield between 3-

10ml of oil on 500ml - Rosemary, Eucalyptus, Lavender,

Clary sage, Manuka, Thyme, Peppermint…….

The smaller one is to collect precious drops – Rose

Geranium, Melissa, Rose, Lemon Verbena, Chamomiles,

Yarrow…..

I pour the hydrosol into my large oil separator. As I do

this, the oil is mixed with the hydrosol again. I watch in

awe as it settles. Millions of miniscule bubbles stream to

the surface. They are tiny drops of essential oil that the

water has released like a sponge being squeezed.

The oil collects at the top, often a golden colour. The

hydrosol settles and clears. At this stage I’m aware of the

energetic lively nature of this process and feel a deep

sense of respect and awe.

A clean beaker is placed at the bottom of the oil separator. I carefully turn on the

tap to release the hydrosol watching carefully to turn off as the oil collects at the

bottom once the hydrosol has been released!

There, now I have my reward, 3ml of precious essential oil!

I will need to distil another 3 times to get my 10mls! However I will also have 2

litres of fragrant Rosemary hydrosol.

There is moisture still in the mix. I don’t want to leave it in as it may cause a bacterial

growth and degrade my oil. I put my test tube with the oil in the freezer. This dries

the oil out and freezes any moisture. I pour the oil off into an amber dripulator

bottle. It goes into my precious collection of my own distilled essential oils.

By this time next year I hope to have 25 of my own distilled oils. I already have 50ml

Eucalyptus, 50 ml Peppermint Eucalyptus, 10 ml Rosemary, 3 ml Lemon Verbena, 10

ml Lime, 10 ml Manuka 10ml Ginger and 10ml Thyme

In spring I will be harvesting German Chamomile, Rosemary before flowering,

Orange, Grapefruit & Lime flowers, spring Manuka and Kanuka, Tarata, Rose

Geranium, Bay leaves, Melissa.

In summer it will be Lavender, Clary sage, Lemon Verbena, Basil, Peppermint,

Helioscrysum, Yarrow, Angelica and some trimming of the citrus as the fruits form

tiny balls – for Petitgrain.

That’s enough!

Comparison

Hydro-Distillation Steam distillation

Plant is subjected to boiling water Plant is subjected to pressure and steam

Distillation is slower and cooler Distillation is fast and hot

Hydrosol is often milky Hydrosol is mostly clear

The distillate shows little essential oil

floating on the surface, most remains in

suspension

Essential oil is evident on top of the

hydrosol and is removed.

Aroma is complex as are the flavours When the oil has been removed, the

aroma of the hydrosol is light and

delicate, the flavour less intense

Nothing has been separated from the

distillate – it remains complete

Has a dual result – Essential oil and the

Hydrosol, however the hydrosol has lost

an element – the essential oil

Every distillation is different depending on season, soil, and climate. This table is an approximate guide to volume’s

and quantities. An idea of plant volume – 3 mature Lavender augustifolia harvested – flowering tops weighs 1kg

approx. Lavender is a high yielding plant. 1kg of flowers yields approx 25-30ml of oil. Most other plants I distil yield a

quarter to half that amount.

Size Plant Quantity Eg Lavender augustifolia Approx Esst Oil yield Hydrosol

5 L Column 250g or 2-3

handfuls

1 mature plant – flowering

tops

1-2ml approx 250-400ml

10 L

Column

500g or 5-6

handfuls

1.5-2 mature plants 3-5ml approx 500-1.5 L

20 L

Column

1.5 – 2 KG 4-6 mature plants 5-15ml approx. 3-5 L

40 L

Column

5 KG 8-10 mature plants 20-50ml approx. 5-10 L

150 L

Column

20-30KG 60-90 mature plants 200-500ml 20-50 L