There are two ways to do this, and they have proper names. Boiling the plant material in the water is hydrodistillation. Putting it in a basket above the water and running steam through it is steam distillation. They are not interchangeable: one gives you more oil, the other gives you better oil, and the difference has been measured. Making essential oils with the Alembic pot still works either way, but picking the wrong method for what you want out of it wastes a run.
Key Takeaways
- Boiling plant material in water is hydrodistillation. Suspending it in a botanicals basket above the water is steam distillation. Hydrodistillation gives higher yield, steam distillation gives a better oil.
- On bay leaf, hydrodistillation returned 0.95% oil against 0.79% for steam distillation, but the steam-distilled oil contained 73 identified compounds against 54, with stronger antimicrobial and antioxidant activity.
- On a water run there is no alcohol to measure, so you stop on smell and volume rather than on an ABV reading.
- A water base needs no licence at all. Distilling water and plant material produces no alcohol and attracts no duty.
- A still over 5 litres needs free ATO permission regardless of what you distil with it, including water and botanicals.
Hydrodistillation or steam distillation: which method
Hydrodistillation means the plant material sits in the water and boils with it. Steam distillation means the plant material sits above the water in a basket, and rising steam passes through it, ruptures the oil cells and carries the oil over. Both run on the same Alembic dome and pot condenser. The basket is the only extra piece of kit that separates them.
| Aspect | Method one: hydrodistillation | Method two: steam distillation |
|---|---|---|
| Where the plant sits | In the boiling water | In the basket, above the water |
| Yield | Higher | Lower |
| Compounds recovered | Fewer | More |
| Oil character | More stewed, more hydrolysis and thermal breakdown | Cleaner, delicate top notes survive |
| Main risk | Scorching if the boiler runs dry | Blockage if botanicals fall into the column |
| Extra kit | None | Botanicals basket |
The measured version of that trade-off comes from a study on bay leaf (Laurus nobilis). Hydrodistillation returned a slightly higher yield at 0.95% against 0.79% for steam distillation, but the steam-distilled oil carried 73 identified compounds against 54, and showed stronger antimicrobial and antioxidant activity. The authors' conclusion is the practical rule: hydrodistillation if you want more oil, steam distillation if you want better oil.
Why does more contact with hot water cost you quality? Three things happen at once in any water or steam distillation: hydrodiffusion, hydrolysis and thermal decomposition. The standard guidance for improving yield and quality is to keep the temperature as low as the process allows and use as little water as you can get away with, which is exactly what a basket does and a boiling pot does not.
For most home runs, use the basket. Hydrodistillation earns its place on tough material, roots, bark, seed and woody stems, where you need the water contact to get anything out at all.
Water base or alcohol base
A water base gives you two separable products: essential oil floating on top and hydrosol underneath. An alcohol base gives you a single concentrated extract that cannot be separated, because the oil dissolves into the ethanol. It holds its aroma longer, which is the argument for it.
For most people the water base is the better choice. It is simpler, cheaper, gives you two usable products instead of one, and needs no licence of any kind, because distilling water and plant material produces no alcohol.
If you want an alcohol base, you need spirit at 40% ABV or below. Buying it is the easy route. Distilling it yourself requires a free excise manufacturer licence from the ATO, and the detail is in our guide to the ATO rules for home distilling.
One thing worth knowing either way: a still over 5 litres needs free ATO permission to own, whatever you distil with it. That permission exists precisely for people running larger stills on water, botanicals and essential oils. A 25 litre Alembic or Turbo 500 boiler is over the threshold, so it needs permission even on a strictly water-base, oils-only setup. Permission to own the still is a separate thing from a licence to distil spirits in it.
Which setup: Alembic dome or Turbo 500 column
The Alembic pot still dome top and condenser is the right tool, because the vapour path is short and wide and runs straight into the condenser arm. A Turbo 500 column can be made to work, but only with the ceramic saddles removed and the reflux coil bypassed, and even then you lose oil to the column wall. Both mount on the same 25 litre boiler.
| Aspect | Alembic dome and pot condenser | Turbo 500 reflux column |
|---|---|---|
| Purpose-built for oils | Yes | No, workaround |
| Vapour path | Short, wide, straight to the condenser arm | Tall, originally packed |
| Prep needed | None | Remove all saddles, bypass the reflux coil and water outlet block, plumb cooling water straight through the condenser |
| Oil loss in transit | Minimal | Oil condenses on the column wall and does not reach the collection vessel |
| Botanicals basket fits | Yes, replaces the stainless steel nut | Yes, threaded section only, in place of the stainless plug |
If you are buying for oils specifically, the Still Spirits Alchemist Series pot still bundles the boiler, dome and condenser. If you already own a Turbo 500 boiler, the dome and condenser alone will bolt straight on. Either way the botanicals basket is the piece that makes steam distillation possible, and there is a wider essential oil distillation range if a purpose-built unit suits you better.
Setting up the dome, condenser and cooling water is the same job whichever method you use, and it is covered step by step in our Alembic pot still instructions. The short version: the cooling water goes in at the end where the distillate comes out, and comes out closest to the thermometer probe. Run the water briefly before you heat anything and check for leaks.
Method one: hydrodistillation, boiling the plant material
Hydrodistillation puts the plant material straight into the water in the boiler. Water volumes depend entirely on the material: as a starting point, 1 kg of rosemary leaf wants about 15 litres of water. If you are using an alcohol base instead, keep it at 40% ABV or below. Collect in small fractions so you can smell where the quality drops, and never take more than 80% of what you charged.
What you need:
- Clean plant material, plus enough water to cover it well
- The 25 litre boiler with the Alembic dome and pot condenser fitted
- Enough 500 ml collection containers for the volume you plan to collect, plus a larger vessel to combine into
- A tall narrow settling vessel, glass, for separating the oil afterwards
- A pipette or dropper
- Cooling water supply and a sink
The steps:
- Load the plant material into the boiler and add water to cover it. Do not pack the material down hard.
- Fit the dome and condenser, insert the thermometer probe, connect the cooling water and check for leaks before applying heat.
- Bring it up to the boil. On a 25 litre charge, expect roughly an hour to reach temperature.
- Once the probe reads 55°C, open the cooling water to about 2.5 litres per minute. Adjust so the distillate runs out as liquid rather than steaming.
- Collect in 500 ml fractions. Label them in order.
- Smell each fraction as it comes off. Quality drops away toward the end and the character turns cooked or stewed. Stop when that happens.
- Stop at 80% of the volume you charged at the absolute latest, so the boiler cannot run dry and scorch the material.
Two things worth planning for. The 80% figure is a ceiling that stops you boiling dry, not a target: most of the oil comes over early, and published trials generally find yield flattening out somewhere around 60 to 90 minutes of active distillation. Chasing the last few litres adds hydrosol and cooked notes, not oil.
And check your vessel maths before you start. Eighty per cent of a 15 litre charge is 12 litres of distillate, which is a lot of jars. In practice, 3 to 4 litres collected in 500 ml fractions is plenty for a 1 kg herb charge, and you will have stopped on smell long before the volume ceiling matters.
Method two: steam distillation with the botanicals basket
Steam distillation suspends the plant material in the botanicals basket above the liquid, so steam passes through it rather than boiling it. This is the method to use for flowers, leaves and anything delicate. It gives a lower yield than hydrodistillation and a cleaner oil, and it removes the risk of scorching the material entirely.
- Add your water, or your 40% ABV or weaker spirit, to the boiler and top up to 25 litres with water.
- Fill the bottom section of the basket with your botanicals. Leave room for steam to move through. Packing it tight creates cold pockets and channels the steam around the material instead of through it.
- Fit the Alembic condenser arm to the dome using the head of the botanicals basket in place of the stainless steel nut. Tighten it properly.
- Insert the thermometer probe and connect the cooling water as normal.
- Turn on the boiler. Allow roughly an hour to reach boiling temperature. Once the probe reads 55°C, open the cooling water to about 2.5 litres per minute.
- Collect into a 5 litre vessel. On an alcohol base, stop when the distillate drops to 20% ABV. On a water base, see the next section.
- Let it settle before you separate anything.
On a Turbo 500 column instead
If a Turbo 500 column is all you have, it will run, with three changes. Take every ceramic saddle out of the column. Assemble it as though you were water distilling, with the cooling water running directly through the condenser and the reflux coil and water outlet block bypassed. Our water distillation instructions for the Turbo 500 cover that plumbing. Then attach only the threaded section of the basket to the condenser column and the underside of the lid, in place of the stainless steel plug, and screw the filled basket in from below once everything is the right way up.
The warning that matters: do not let botanicals fall into the condenser column. A blockage in a column is not something to poke at. If it happens, call us before you try to clear it yourself.
Cleaning between runs
Clean the boiler, dome, condenser and basket thoroughly after every oils run, and do it before the residue dries. Essential oil residue is stubborn and it carries over. A rosemary run followed by a lavender run in an uncleaned still gives you rosemary-lavender, and if you use the same boiler for spirits, it gives your next gin an off note you will not be able to place. Warm water and a purpose-made cleaner, then a rinse and a dry.
When to stop collecting
On an alcohol-base run, stop when the distillate falls to 20% ABV. On a water-base run there is no alcohol in the still and nothing for an alcometer to read, so you stop on volume and on smell instead.
Three signals to stop a water run:
- Smell. Take a 500 ml fraction, smell it, and set it aside. When a fraction comes off smelling cooked, flat or vegetal rather than aromatic, the useful part is over.
- Visible oil. Hold each fraction up. When you stop seeing oil beading on the surface, you are collecting hydrosol and not much else.
- Volume. Never exceed 80% of what you charged, so the boiler cannot run dry.
The fractions are also worth keeping separate rather than combining blind. Early and late fractions have different compositions, and the early ones usually carry the top notes.
Separating the oil and saving the hydrosol
Let the distillate stand undisturbed in a tall narrow glass vessel, then lift the oil off the surface with a pipette. Narrow matters: the same volume of oil forms a thicker, more workable layer in a tall vessel than a wide one. Most oils float, though a few, clove and cinnamon leaf among them, are denser than water and settle on the bottom instead.
What is left is hydrosol, and it is not waste. Rose water and lavender water are hydrosols. So are witch hazel, chamomile and orange blossom waters. On a low-yielding botanical the hydrosol may well be the more useful of the two products, and it keeps for months refrigerated in a sealed bottle.
If you ran an alcohol base, there is nothing to separate. The oil is in solution with the ethanol and the distillate gets used as it comes off.
What yield to expect
Yields are low. Published figures put lavender's whole flowering top at around 0.7% and fresh rosemary at 0.5 to 1%. Those are laboratory and commercial numbers on efficient equipment, so a converted spirit still will return less. Expect single-digit millilitres of oil from a kilo of herb.
| Botanical | Typical oil yield | Oil from 1 kg |
|---|---|---|
| Lavender, whole flowering top | ~0.7% | ~7 ml |
| Lavender, calyx only | ~1.3% | ~13 ml |
| Rosemary, dried leaf | 1 to 2% | 10 to 20 ml |
| Rosemary, fresh | 0.5 to 1% | 5 to 10 ml |
| Peppermint, dried leaf | 1 to 2% typical | 10 to 20 ml |
| Tea tree | 1 to 2% | 10 to 20 ml |
| Thyme, dried | 0.5 to 2.5% | 5 to 25 ml |
| Rose petals | 0.01 to 0.02% | 0.1 to 0.2 ml |
The lavender rows are the interesting pair, and they point at something more useful than any distilling technique. A study on cultivated Lavandula angustifolia found the calyx yields around 1.3% oil while the whole flowering top, which includes stem and leaf, yields about 0.7%. Nearly all the oil is in the calyx. Stripping the calyces rather than throwing whole cut stems into the basket roughly doubles your yield per kilo, and no adjustment to the still will do that for you.
The rose row is there as a reality check. At 0.01 to 0.02%, a kilo of rose petals gives you a couple of drops. That is not a technique problem, it is why rose oil costs what it costs.
Frequently asked questions
Can I distil essential oils in a Turbo 500? Yes, with the ceramic saddles removed and the reflux coil bypassed, and with only the threaded section of the botanicals basket fitted in place of the stainless plug. It works, but the tall column costs you oil that condenses on the wall and never reaches the collection vessel. The Alembic dome and pot condenser on the same boiler is the better setup.
Do I need a licence to distil essential oils in Australia? No. Distilling water and plant material needs no licence at all. You do need free ATO permission to own a still over 5 litres, and that applies whatever you distil with it. An alcohol base is the only route that brings excise into it, because of the spirit rather than the oils.
Why is my yield so low? Probably the material, not the method. Most herbs sit between 0.5% and 2% oil by weight, and a lot of that oil is concentrated in specific parts of the plant. On lavender the calyx holds nearly all of it, so distilling whole cut stems halves your return before you even turn the boiler on.
Can I use the same still for spirits and essential oils? Yes, but clean it thoroughly in between. Essential oil residue carries over and it is persistent. If the boiler goes straight from a rosemary run to a gin run, you will taste the rosemary.
What do I do with the leftover water? That is hydrosol, and it is a product in its own right. Rose water and lavender water are exactly this. Bottle it, refrigerate it, and it will keep for months.
Where to start
Making essential oils at home comes down to one decision made before you pick the plant. If you want the most oil out of tough material, hydrodistillation and a boiling charge. If you want the best oil out of flowers and leaves, the botanicals basket and steam. Then set your stopping point: 20% ABV on an alcohol run, smell and volume on a water run.
On kit, the Alembic pot still range is where to look if you are starting from nothing, and the dome and condenser alone will fit a Turbo 500 boiler you already own. If oils are the whole point of the purchase rather than a side project, the essential oil distillation range has purpose-built units worth comparing first.
