Here are answers to some questions about stills, distillation and extraction. This section was primarily created to provide answers to novice distillers, but more experienced distillers might still be able to find some interesting elements here. 
If you do not find the answer to a general question you have about stills, distillation and extraction, fell free to ask us using the contact form below. If we can give an answer and if we think it could be interesting to add it here, we will.
This section is not static, some Q&A will be added and some answers may be revised over time. Also, please note that I (Benoit Roger) answer to these questions as honestly as possible and to the best of my knowledge and experience but some questions are not easy to answer in a few words and we simply have no answer yet for others.   


What is an alembic, a still, and a distiller?
Alembic and still both refer to the equipment used to distill plants or alcohol. We usually use the term alembic when we talk about a traditional apparatus made from copper. Most of the time, these alembics are composed of a pot, an onion-shape head with a swan neck and a serpentine condenser. Between the pot and the head, we also sometimes see a column, mostly used for steam distillation of aromatic plants.

Oppositely, a modern stainless unit composed of a cylindrical tank, a lid and a shell and tube condenser is usually called a still. That being said, these differences do not seem to be official, the alembic and the still both refer to a similar equipment used for similar purposes and they are often used interchangeably. In french, a traditional copper alembic and a modern stainless still are both called ''alambic''.

As for the distiller, many people use this term to design the apparatus used to distill but if you look at the definition in the Oxford and the Cambridge dictionaries, both refer to ‘’the person or the company’’ who or that uses the still, or the alembic, to produce strong alcohol. We can assume that a person using a still or an alembic to produce essential oils or hydrolats would also be called a distiller.
What are the different parts of the still and their functions?
A modern still designed for the essential oils and hydrolats distillation is composed of the following parts:

- The tank. It usually has a cylindrical shape and it is often taller than wide unless the still is primarily designed for water distillation (more details below). This is where we put the plant material we distill. When the still is designed for steam distillation, we should have inside a grid or a basket to support the plant material above the bottom of the tank or the water in it. The tank can be insulated or not and it can be equipped with electric heating elements and/or a steam jacket, a steam coil or a steam injection port when it is used with a satellite boiler. A heating source such as a steam jacket/coil at the bottom of the still is mandatory to perform water distillation while the steam injection port is mostly used for steam distillation.

- The lid. It can be flat, conical or have a dome shape. Its purpose is obviously to close the tank during the distillation so that all the steam reaches the condenser. A still designed for water distillation sometimes just has a manhole to load the water and the plant material but a still designed for steam distillation should have a full lid allowing a complete opening of the tank. This allows an easier loading, homogeneous compaction and unloading of the plant material. The lid can be sealed to the tank by an hydraulic joint, an O-ring or a gasket made from different material (more details below).

- The steam outlet connected to the condenser. It is preferably connected to the lid but it can also be connected to the top of the tank, especially when the lid is on an hinge. The diameter of this connection must be calculated so that the steam gets out of the tank without inducing a significant back pressure.

- The condenser. Its purpose is to condense then cool down the vapors coming from the tank. It can be a serpentine or a shell and tube condenser. The pro and cons of these two types of condensers are discussed in a section below.

- The Florentine flask used to separate the essential oil from the hydrolat. As for the condenser we enter in more details in a section below.
Can we use an alcohol still to make essential oils and reciprocally?
The short answer is yes as long as they are both designed to boil, condense and cool down vapors into a liquid. However, depending on the design of the stills and according to the points exposed just below, the results may not be ideal, both in term of yield and quality when using an alcohol still to make essential oils and reciprocally. This question is relatively complex but the section below brings some information about what differentiate an still primarily designed to distill alcohol or essential oils and hydrolats.
Essential oil still vs. alcohol still, what are the differences?
Several elements differentiate a still primarily designed for alcohol or essential oils and hydrolats distillation:

- The opening of an alcohol still is often relatively small, especially when it is designed to distill a mash or any fermented liquid solution. In this case, no need of a complete opening as the distilled liquid can be drained after the distillation using a valve at the bottom of the tank. Note that this is not true for the stills designed to distill fermented fruits which are usually equipped with a complete opening and lid. A still designed for steam distillation should always have a complete opening to allow an easy loading, compaction and unloading of the plant material.

- The hat, head, column or goose neck of an alcohol still are usually designed to get some reflux thanks to a larger and non-insulated surface (onion or high conical head). In essential oil distillation, we usually do not want any reflux, thus the surfaces are minimized and the lid and column are preferably insulated.

- The condenser: the evaporation of 1 L of water requires about 3 times more energy than the evaporation of 1 L of ethanol. The same applies for the condensation: 3 times more heat must be removed from the vapors to condense 1 L of liquid water compared to the same volume of liquid ethanol. This obviously has an impact on the design and capacity of the condenser.

- The alcohol still does not require a Florentine flask; the essential oil still does.

- In the industry, most of the essential oil stills are made from stainless while alcohol stills are made from copper (at least some parts). We will get back to this point below.
Copper still vs. stainless steel still vs. glass still, which one is the best?
Not an easy one... but coming soon
What is the ideal still tank shape and height/width ratio?
Besides the small glass units, copper or stainless stills usually have a spherical or a cylindrical shape (we will not consider the large container stills here).

For water distillation, both the spherical and cylindrical pot/tank can be used. For steam distillation, the best tank shape is certainly the cylinder as it allows a better distribution of the steam rising through le plant material. With a spherical pot/tank in steam distillation, the loading, even compaction and unloading are not convenient and the steam, when it reaches the plant vessel in the center tends to rise through the plant unevenly (mostly through the center).

As for the height/width ratio, there is probably no strict ideal ratio for water or steam distillation, however and as mentioned in old texts written by very respected authors such as E. Guenther and EFK Denny, there are still important practical considerations when choosing the height/width ratio for a still:

For water distillation, an important point is that the plant material must move freely in the boiling water and not being compacted against the bottom of the still, thus a too narrow and high unit is not ideal and we generally prefer still tanks that are slightly larger than high. Considering the free movement of the plant in the still, a spherical pot is probably even better than a cylindrical tank but at similar dimensions, the difference is probably very subtle (no data found about this specific point).

For steam distillation, this is the contrary, we generally prefer a still tank that is higher than wide. Here, one important factor is that the steam must reach a certain velocity to get a good contact with the plant material, especially if the compaction is not perfectly homogeneous. Considering this, and to reach the same steam velocity, a still which is higher than wide will need considerably less steam than another still of the same volume which is larger that high. Also, in the still with a higher height/width ratio, as the steam travels at the same speed but rises through a higher plant charge, it will also stay longer in contact with the plant material and should be able to distill the plant material more efficiently. That being said, a still which would be 10 times higher than wide would be totally impractical. That is why when a still is specifically designed for steam distillation, it is usually about 1.5 to 2 time higher than wide. This seems to be a good compromise.
Tilting or static still, what is the best?
At small scale, static units are perfectly fine as long as the user can lift the empty still. But when we reach 250-500 L, the still cannot be manipulated as easily as a 25 L unit.

A good option if we have several big stills in a raw that we want to use for steam distillation is to have a common system for the loading and unloading of the plant material, which typically is a monorail and one or several trolley hoists. But for an isolated unit between 250 and 500 L designed for steam distillation, the tilting option is interesting. It does not help for the loading which must be done manually or with a chipper/blower but the unloading is quick and easy, and we do not need the high ceiling required with the monorail/hoist installation.

At large scale (2000 L and over), the tilting option is still possible but the still must be heavily built to keep its perfect round section with repeated tilting. A slight deformation may induce some tightness problem between the tank and the lid. Also when the still is equipped with a steam jacket, we may have to disconnect the piping each time it is tilted. This is possible but not convenient. Finally having a monorail/hoist above a big still is also a big advantage for loading large quantity of plant material.

So, to summary, at small scale, the simpler the better, static units are fine, at medium scale for an isolated unit designed for steam distillation, the tilting option is interesting and at large scale or with several stills in a row, the monorail/hoist option may be advantageous.
What is called the reflux?
The reflux is the vapors condensing on the cold inner surface of the still before they reach the condenser. These condensed vapors composed of liquid water and some essential oil flow back in the plant charge and eventually reach the bottom of the still under the plant material (for steam distillation).

Having some reflux at the beginning of the distillation during the warming up phase is almost inevitable, and it is not a problem. However, an excessive reflux during the whole distillation is generally something we try to avoid as it comes with a waste of energy, it lowers the essential oil yield or lengthen the distillation time, it can also be detrimental for the essential oil quality, i.e. more hydrolysis, more still notes, etc.

For alcohol distillation, a certain reflux is required to purify the alcohol and a good and controlled reflux at the top of a column is required to get neutral alcohol (95°+ ethanol).
Is it important to distill with an insulated still?
The insulation of the tank, lid and column is usually a good thing for essential oil distillation as it significantly reduces the reflux during the distillation thus increases its efficiency. However, its impact will be more or less noticeable depending on the still environment. Obviously, if a still is operated outside with wind, and cold temperature, rain or even snow, the insulation is almost mandatory.

On the other hand, if the still is operated inside with a low air circulation at 25°C, the insulation may not make a great difference on the distillation efficiency. That being said, when the working space is already hot, it may be interesting to not heat it more. In this case the insulation may be interesting for the distiller (the operator, not the still) as well as for his/her safety (protected hot surfaces equal less chance of burn). Note that this insulation is even more important for the small units than the big ones as the small units have a higher surface/volume ratio and that the ideal humidity during a distillation is not the same for all plants.
What is the best sealing solution between the tank and the lid or hat?
There are different possible sealing options between the pot or the tank and the lid of the still.:

On the small to medium copper alembics, as the copper is usually thin and flexible, the sealing is generally made by the direct insertion of the copper hat in the pot. If the metal-metal joint is not good enough, the traditional way to seal these two pieces is to apply a freshly made rye paste on that junction. A modern and much faster way to seal a copper pot to its head is to wrap the junction with large Teflon tape. Given the poor biodegradability of Teflon, we encourage you to reuse your Teflon as long as possible before throwing it away.

On large traditional units, we still often see what we call a water seal. The principal is that the lid stands in a kind of circular gutter filled with water. If some steam condenses on the lid and flows down into the gutter, it eventually flows back in the pot or the tank as the inner edge of this gutter is lower than the outer one. The advantages of this water sealing is that it is simple, it works even though the lid and pot or tank do not match perfectly and you have no seal to replace ever. The disadvantage is that a small difference in pressure in and out of the still will push the water out of the still or suck it inside.

Finally, some still also use a seal made from different material. This seal can have a flat, square or round section (for the two latters we talk about ‘’O-rings’’). A good seal is not too hard, resilient, water and steam resistant and also resist to the products you are distilling (essential oils or alcohol). The perfect seal that is not expensive and works in absolutely every situations is almost impossible to find. Here are still a few materials that we tested and work fine in most of the situations:
- Silicone: It can be food grade, it stands steam and pretty high temperature, it can last years and stays soft and flexible. However, it can temporarily swell with some essential oils (I observed this with a rectification of a thujones rich essential oil).
- EPDM: It is common thus not very expensive, it stands steam and temperature and it can last years. However, it tends to stick to the metal (silicone does not) and it is less resilient than Silicone. Some intensive uses with specific essential oils can also result in a temporarily stretch out of EPDM O-ring (it has been observed with some lavandin distillations).
- Nitrile/Buna: Even if there are different qualities and compositions, Buna O-ring tend to stretch in contact with the steam, thus this is not a material we recommend between the tank and the lid.
- Neoprene: It generally does not stand temperature and steam as good as Silicone or EPDM thus neoprene this is not a material we recommend between the tank and the lid.
- Viton: As a fluoropolymer, it usually has an excellent chemical resistance but it is expensive and all the Viton O-rings do not stand steam. It is a good option if we have to work (distillation or reflux extraction) with harsh organic solvents but probably not the best choice for water or steam distillation.
Serpentine condenser vs. shotgun or shell and tubes condenser, which one is the best?
The classic serpentine condenser is composed of a long coiled tube in a water tank usually open at the top. In a shell and tube or shotgun condenser, this long tube is cut in several straight sections which are welded in parallel in a bigger one where the cold water is injected.

Among the advantages of the serpentine condenser, they are easier to build. As they contain much more water, they also offer a much greater inertia which may be convenient if we do not have a continuous water supply for the condenser. On the disadvantages side, they require much more space as the whole serpentine condenser is usually almost as big as the tank itself. It is generally not supported by the tank so it must stand beside at the exact right height and position which sometimes requires some fine tuning. As serpentine condensers are usually open at the top, they easily overflow if the outlet hose offers a bit too much restriction or if it is too high. And among the biggest disadvantages, we cannot use a too small coiled tube with a big still (it would generate to much back pressure), but we cannot coil a big tube either, thus serpentine condensers cannot easily be used for big stills. They are usually only used for small to medium stills. Also as all the steam enters in one relatively small tube, they are more prone to generate back pressure in the still, thus leak between the pot or tank and the lid. Finally, as the serpentine condenser is made of a long coiled tube, it is much more difficult to clean.

The shell and tube condensers or shotgun condensers are more technical to design and build. They also require a continuous water supply but they offer numerous advantages: they take much less space, they are completely closed so they cannot overflow like open serpentine condensers, they can suite all kind of still sizes including the bigger ones, they usually generate less back pressure (if they are well designed) and they are much easier to clean. Another advantage is that the surface area can be ‘’tuned’’ by blocking a certain proportion of the tubes inside (just be careful with that, it must be done wisely).
Vertical or oblique shotgun condenser. What is the best?
We see both vertical and oblique shotgun condensers in the industry. While the oblique position may come with certain advantages about the space occupation (they may be installed lower), experiments show that a vertical shotgun condenser is more efficient than the same in oblique position.

To understand why, let’s imagine some steam condensing at the top of a vertical condenser tube. After the condensation, the liquid would flow down on the entire inner surface of the tube. Now let’s imagine the same with an oblique condenser tube (almost horizontal). After the condensation, the liquid would gather at the bottom of the tube and flow down in straight line, thus it would use a much smaller inner surface of the tube in the cooling phase, which makes the heat transfer much less efficient. This is, at least, the best explanation I have found so far.

Another disadvantage for the oblique condenser is that it requires inner baffles to work properly. Otherwise the hot water settles up and the cold water settles down, thus the cooling would be good in the lower tubes but insufficient in the upper ones.
Can we use another kind of condenser besides serpentine and shotgun condensers for distillation?
Yes, at small scale (under 5-10 L), a glass condenser can be a good choice but it must also be chosen wisely and used adequately:
For vertical use, a Liebig (straight inner tube) or a Allihn (inner tube with a series of bubbles) condenser are a good choice. The Allihn condenser offers a slightly larger surface area for the same length than the Liebig condenser but it is also a bit more difficult to clean. For an oblique use with a very low inclination, we do not recommend the Allihn condenser because some distillate will stay stuck in the bubbles. This is not a big problem but not something we want either. The Allihn condenser is also a good choice when used as a reflux condenser (when the vapors enter at the bottom of the condenser and the condensate flows down to the bottom too).

We do not recommend using coiled glass condensers (Graham, Coil, Dimroth, Friedrichs), they are efficient but more fragile and harder to clean. Note that the Graham condenser should never be used as a reflux condenser. The glass condensers are an interesting option at small scale, and this is always interesting to see the condensation process. The main problem is that they break quite easily. They also have a low thermal conductivity which make them relatively inefficient.

At larger scale, we sometime see the equivalent of a Coil or Dimroth condensers (coolant inside a coiled tube) made with a coiled metallic tube. They can be efficient but quite difficult to clean, especially if they cannot be dismantled.

We sometimes see (or have seen in the past) ‘’zig-zag’’ condensers. The way they are built solves one of the biggest problems of the serpentine condenser as we can easily start with a large section of tube and reduce the tube diameter progressively in the elbows. The big problem however with this type of condensers is that they are almost impossible to clean.

Finally, at very big scale (container stills), we often see stainless condensers made with a very large number of thin tubes twisted on themselves. Given their very large heat exchange surface, they offer good results but they may generate some back pressure given the size of the tubes and they are more difficult to clean as the tubes are very small and not straight.
Can I use any kind of Florentine flask to separate any essential oil on any still?
No, we cannot. Some essential oils have a specific gravity significantly lower than 1, which means that 1 L of essential oil is lighter than 1 L of water (8-900 g instead of 1 kg), thus they float. In this case we need a Florentine flask for ‘’light oils’’ (not the most accurate term but this is how we call them in the field) which accumulate the essential oil at the top.

In some other cases, especially when the essential oils are rich in phenolic compounds, their specific gravity are higher than 1 and they sink in the water. In this case we need a Florentine flask for ‘’heavy oils’’ which accumulates the essential oil at the bottom.

Also, some essential oils decant much more slowly than others and require a large Florentine flask in which the hydrolat moves relatively slowly. The size of the Florentine flask obviously has to fit with the size of the still, or more accurately the distillate flow. We cannot use a too small Florentine flask with a big still, otherwise the essential oil will not have enough time to fully separate and will get out with the fast flow of hydrolat. Oppositely, a too large condenser is not a good thing either as the small amount of essential oil may be lost on the Florentine flask and its larger inner surface.

Finally, a lot of details in the design of the Florentine flask may help in the separation of the essential oil and hydrolat but this question cannot be discussed in just a few lines.
What is a ‘’casse-essence’’?
To the best of my knowledge, there is no English word for that piece and to be fair, I have never found it in books. This is the kind of thing we learn by oral transmission from knowledgeable people working in the field for a long time.

A ‘’casse-essence’’ is a piece of equipment used with the Florentine flask and designed to enhance the separation of the essential oil from the hydrolat. This is a kind of funnel with a modified stem designed to redirect the distillate flow upward in the Florentine flask. It both prevents the distillate flow to break the essential oil layer when the distillate drops in it and helps the essential oil to reach the surface of the hydrolat where it accumulates. Note that it is only used with ‘’light’’ essential oils (for essential oils with a specific gravity lower than 1, see the previous point for more explanation on that point).
How much energy do I need to run my still?
When we distill plants, we need some energy to boil the water in the still or in a separate boiler used to produce steam. But how much energy do we need exactly?

Depending on the heating system, the question is more or less complex as a certain proportion of the energy may be lost. Typically, when we use a propane burner to boil the water in the still, the combustion does not happen in a closed system and a certain proportion of the heat is lost. This lose can be contained if the system is well designed and if no external element (like wind) disturbs the heating of the still. On the other hand, if the still is heated by a propane burner or a wood fire and the wind constantly blows on the fire, a much greater proportion of the heat may be lost, even if the still is insulated. Oppositely, when a still is heated by internal electric elements, or if an electric steam generator is used, the energy lose is much lower.

Theoretically (without any heat lose), boiling 10 L of water already at 100°C requires 22 570 kJ or 6.27 kWh. Similarly, and again if we had absolutely no heat lose, a 4.5 kW electric heating element (the one installed in the Explorer) should boil about 7.2 L in one hour of constant heating. In real life, 1 hour of constant heating with a 4.5 kW element in a non insulated Explorer allows to boil 6.0 L of water per hour (water already at 100 degree). With the same setup but an insulated Explorer, we boil 6.2 L of water per hour. The difference between the theoretical and the real value comes from multiple causes such as the heat loss of the still, electric losses in the cables and regulator as well as the real power of the elements and the real voltage you get at the electric plug which is not exactly 220 or 110 V.

When heating with a propane burner, with the same still (non insulated Explorer), we need about 0.8 kg of propane to boil 6.0 L of water already at 100°C. With a complete combustion, 0.8 kg of propane should provide about 40 000 kJ of heat thus in theory, if all the heat were reaching the water in the still, we would boil 17.7 L of water (already at 100°C). As you can see the energy loss is much higher when heating a still externally with a propane burner. That is expected and could be much worse in cold and windy conditions (here the tests were done inside at 24°C).
What is the best solution to heat a still for essential oil and hydrolat distillation?
You have several possibilities when it comes to heat a still or a satellite boiler used to generate steam for a distillation:

- Wood: With the next to be enumerated, it is obviously the most traditional way to heat a still. Wood has the advantage of proving a lot of heat and depending on the distillation area, it can be readily accessible. The drawbacks of burning wood to distill is that you have to build a stove to sit the still on and collect the fume. It is also much less easy to regulate than other energy source and you cannot lower the heat as quickly as a propane burner or an electric system, thus it requires an extensive experience.

- Distilled plant material: As we only keep around 1% of the plant when we distill for essential oils, using distilled biomass as a source of energy is an interesting solution to both use the plant completely and reduce waste. In addition to the same drawbacks as wood, another one is that the distilled plant material must be dried to be used as a fuel.

- Natural gas: As wood, it provides a lot of heat and it is portable (at small scale.) It is also much cleaner than wood thus you do not require to make a stove with a chimney for the fumes. At small scale the burner is used as the stand and at large scale, the burners can be attached to the bottom of the still. The main drawback of gas for heating a still is that it is not suitable for any indoor environment. For example, and for obvious safety reasons, you cannot have flammable products like essential oils or alcohol stored next to a still running with a propane burner.

- Electric hotplate: It is a good solution at small or very small scale, but a classic hotplate is usually not powerful enough to get a good distillation flow with a still above 20-30 L. A good solution however at medium scale (around 40 L) is to use an infrared electric plate. A 3 kW infrared burner allos to get a good distillation flow with a 40 L still (with a black coated bottom). Above that scale, this is not a suitable solution.

- Electric element(s): They are excellent in term of efficiency, they are clean, safe, fast responding, easy to operate and work in almost any environment. The drawbacks are the lack of portability; they obviously have to be connected to the power network unless you produce yourself enough electricity (and it needs a lot of it). The other drawback is that internal electric elements are good for “water and steam distillation” (= boiling water at the bottom of the still to perform steam distillation) but they are not recommended in water distillation as the contact between the plant and the resistance must be avoided to not burn both of them. At small scale, a complete electric heating system including the power regulator is also much more expensive than a propane burner.

- Steam jacket: this is now the most common way to heat an industrial still. The steam jacket is a sort of closed false bottom in which pressurized steam is injected. We generally inject steam at 3 to 4 bars (= 145-150°C), the steam is trapped in the steam jacket until it condenses then the condensate is automatically drained so that almost all the energy coming from the condensation of the steam is transferred to the water inside the still. With this method, there is no fire hazard and it can be used at almost any scale, but it requires a pressurized steam boiler which is usually very expensive.
Can I distill essential oil using a ”bain-Marie”?
If the still and the “bain-Marie” or water bath are operated at the same pressure (usually normal pressure), no you cannot as the water in the water bath and the water in the still would boil at the same temperature and any heat transfer requires a difference in temperature. This comes from the second law of thermodynamics. Even if the water in the water bath is vigorously boiling, the most it can do is to bring the water in the still close to its boiling point. Once it is, the water bath and the water in the still are almost at the same temperature and the heat transfer almost stops, then the water in the still does not boil.

Note that it is a completely different thing if you distill alcohol which does not boil at the same temperature as water. In this case, a water bath is a very good and gentle heating solution.

It is also possible to distill water with a water bath if the still is operated under vacuum as in this case, the water in the still would boil at a lower temperature.
Why the design of a still is important?
The design of a still may have an influence on various aspects of the distillation process among which the safety, the efficiency, the yield and quality of the essential oil and hydrolat, the ease to use the still and to clean everything, its durability, etc…

- Safety: A well designed still should be safe to use. The steam outlet, the condenser and the distillate outlet should not be too narrow. The steam should be able to escape freely without generating a significant back pressure in the tank (see next point). The still should also be stable and tilting units should be wisely designed to ensure that the user cannot be hurt one way or another.

- Efficiency and essential oil yield: A well designed still should be efficient with the great majority of plant material. In the case of essential oil distillation, it means it should give the expected yield with the least amount of energy and water for the condenser. Several parameters may affect the efficiency and essential oil yield among which the metal type and thickness, the geometry of the whole unit, the insulation, the tightness, the type, design and position of the condenser, the adequacy between the condenser and the steam flow, the Florentine flask size and geometry (and unfortunately the ideal one may not be the same for all the essential oils), etc… The possibility to cohobate is also interesting for long distillation or for essential oil that hardly separate from the hydrolat. It may improve the yield and give a more complete essential oil that contains more of the polar constituents.

- Ease to use and regulate: A well designed still should be easy to use and regulate. Among the important parameters here we could mention the complete opening (complete lid) which is almost necessary for steam distillation (much easier loading, compaction and unloading of the plant material), the removable grid for steam distillation (being able to adjust the height is a plus), the drain valve adequately dimensioned for the size of the still and the distilled plant material, the condenser size and the water regulation system for the condenser, automation, the design of the Florentine flask, etc.

- Ease to disassemble and clean: The cleaning process between the distillation of two different plants is critical for the purity, thus quality of the essential oils and hydrolats you distill. That is why it is important to be able to disassemble the still completely and especially the condenser to be able to do a perfect manual cleaning. In that regard, the shell and tube or shotgun condensers (when we have a free access to both the inlet and the outlet) are much easier to clean than any other condensers as all the inner tubes can be manually whipped and checked.

- Durability: if we talk about chemical resistance, glass is probably the best material a still can be made of. But glass breaks easily and it is not easy to repair. Thus, unless you work at very low scale, a metal still is usually more durable. Now the most common material used to build a still are stainless steel and copper. Stainless steel is arguably more durable than copper as copper easily oxidize in boiling water but a copper still made with a good metal thickness which is properly used, cleaned and stored can last a very long time. A good stainless still will last a life without any problem if it is build from a proper stainless grade and if the metal thickness is adequate. Still tanks made too lightly (too thin) may deform over time which may induce some problems of tightness.
What should I check if I want to use an home-made still?
If you have the possibility to use an home made still, please check a few things before going ahead. Distilling aromatic plants, especially the first time, is a wonderful experience and doing mistakes is part of the learning process but there is one point you should never play with: your safety and the safety of everyone around the still.

The main risk with a home made still is to build pressure inside the pot/tank when distilling because of a poor design. If this happens, the still may explode and everyone beside it may be badly burnt or injured. This may happen if the steam outlet on the lid or the tank is too small for the steam flow or if something blocks the steam or the distillate (I have seen a tutorial on YouTube explaining ‘’how to build your own still’’ where the ‘’designer’’ proposes to install a valve at the distillate outlet and just open it when the distillation has begun… This is super dangerous!!!). So here are a few important verifications if you want to use a small homemade still:

- Check that nothing may block the steam or the distillate outlet (no valve, no squeezed outlet tube, etc.)

- Check that the plant material in the tank cannot block the steam outlet (some plant material) may expand with the steam).

- Make sure that the diameter of the steam outlet and the coiled tube of the condenser (if it is a serpentine condenser) is at least 3/4” for a 50 L still and at least 1’’ for a 100 L still. When we push steam in a tube at a higher speed than 20 m/s, the back pressure rises quickly!
Is there any pressure in the still during a distillation?
In normal conditions with a still designed to work at ambient pressure (and if it is well designed, see the previous section), you should not have a significant pressure difference between the inside and the outside of the still. The steam should always be able to escape freely from the still.

Now if the plant material is (too) heavily compacted in the still and if the steam flow is relatively high, you may have a small pressure difference below and above it inside the still, but this pressure difference is usually low. And if the condenser is designed adequately for the steam flow, it should not generate a significant back pressure thus the pressure above the plant and outside the still should be almost identical.

Note that serpentine condensers tend to generate more back pressure as all the steam must enter in one relatively small tube.
Can I distill under pressure or under vacuum with my still?
If the still is not designed to be used under vacuum or under pressure, no you cannot and you should not modify it yourself to do so as it may destroy your still and hurt the user.

In vacuum distillation everything from the still tank to the receiver for the hydrolat must be under vacuum and all the parts must be designed so that there is no leak between them (obviously) and so that they cannot crush on themselves (especially for the tank and the receiver).

In pressurized distillation, there is an adjustable steam restriction between the tank and the condenser which creates a back pressure in the tank and the later one must be designed to hold the pressure.

These two types of units require a certain expertise in the design and building as well as skills when using them.
Am I allowed to purchase a still?
This one really depends on your location. In Canada “It is not prohibited to possess a still that is to be used for purposes other than the production of spirits, such as the purification of water. There is no licence or registration required under the Act to possess a still for uses other than the production of spirits.” From the excise duty memorandum EDM3-1-1-23.

If the plan is to produce some alcohol in Canada, this is another project requiring registrations and licences.

If you are outside of the Canada, we strongly recommend you to check the laws in force in your country or state before importing or purchasing a still.


How do we produce essential oils and hydrolats
According to the ISO 9235:2021, an essential oil is a "product obtained from a natural raw material of plant origin, by steam distillation, by mechanical processes from the epicarp of citrus fruits or by dry distillation, after separation of the aqueous phase - if any - by physical processes".

It then precises that "the essential oil can undergo physical treatments which do not result in any significant change in its composition (e.g. filtration, decantation, centrifugation)".

Later in the standard, the distinction is made between water distillation and steam distillation (see next point).
What is water distillation and steam distillation?
Water distillation and steam distillation are the two main technics used to produce essential oils and hydrolats.

In water distillation, the plant material is boiled with and in the water to get the essential oil and the hydrolate. For instance, rose flowers, ground iris rhizomes and oleoresins are usually distilled by water distillation.

In steam distillation, the plant material is not immersed and boiled in the water. Instead, it is loaded as such into the still on a grid and steam is injected (or produced) under the grid so that it rizes through the plant material. In this case, the plant material is only in contact with the steam but not with boiling water as in water distillation. Plants such as lavender, mint and conifer needles are usually distilled by steam distillation.

Some plant materials are preferably distilled by steam distillation, others by water distillation. See next point to know which technic is preferably used for which plant material.
When should I use water distillation or steam distillation?
If you primarily distill a plant for its essential oil, steam distillation should be considered first as it generally gives good results (EO yield and quality), it is faster, you can put more plant material in the still and it requires less energy than water distillation. However oleoresins, some wood/bark sawdust, some crushed seeds or rhizomes and some very fragile flowers cannot easily be distilled by steam distillation because steam cannot go through the plant material homogeneously (it melts or swells and get compact then steam escapes by some channels and the plant material is poorly distilled). In these cases, water distillation should be considered.

It should also be noted that some hydrolats distillers sometimes prefer water distillation over steam distillation for some plants even if steam distillation is possible. Try and compare is probably the best advise we can give you here.
How to load the plant material in the still for a steam distillation?
In steam distillation, the plant material is loaded as such in the still, on a grid. The most important point here is to get an homogeneous disposition and compaction in the still so that the steam rises homogeneously through the plant material. If the compaction is not homogeneous or if there are some unoccupied areas, the steam will escape using the easiest path and some of the plant material may be poorly distilled resulting in a low yield or a longer distillation.

As for the ideal compaction, it depends on the plant material, but a good strength can generally be applied on plants with a good ‘’structure’’ (conifer needles for instance) if they are not turned into a fine powder. On the other side, plants with much less structure (soft leaves or flowers) or finely crushed plant material should not be compacted with too much strength as they already tend to compack themselves during the distillation and may clog more easily.

A good way to load a still for steam distillation is to put some plant material, make sure it is evenly distributated, apply some compaction and keep layering this way up to the top. Particular attention should be paid to the edges of the layers, between the plant material and the wall of the tank. It is very important that there is no gap here, then if needed, put additional plant material to fill any gap and compact well.
What ratio plant/water should I use for a water distillation?
From a general point of view, when we perform a water distillation, we usually want the plant material to be able to freely move within the boiling water during the distillation which means that we must have much more water than the plant material we distill. Now the exact plant/water ratio depends, as always, on the plant we distill.

Some plant material like dry ground iris rhizomes powder will absorb a lot of water for their weight during the distillation so we have to start with a relatively low plant/water ratio like 1/15 (1 kg of plant material for 15 L of water).

Other plant materials like fresh rose flowers will not absorb much water so we can start with a higher plant/water ratio such as 1/5 (1 kg of plant material for 15 L of water).

A point to consider is also the length of the distillation. For a plant material that requires a very long distillation time and if we do not cohobate (see below what it means) we have to put an excess of water so that we still have a reasonable ratio at the end of the distillation. If we start with a too high plant/water ratio, we can always add some water in the still (if the still allows it) during the distillation but adding cold water would stop the distillation for a few minutes which is generally something we do not want. In this case, we preferably add very hot or preboiled water.
What is cohobation?
Distilling with cohobation simply means that we continuously reinject the hydrolat in the still right after the separation of the essential oil in the florentine flask.

It is obviously not something we do when we distill for the hydrolat or when we both want to keep the essential oil and the hydrolat. However, it can be interesting if we do not want to keep the hydrolat and if:
- We have a very long hydrodistillation (Iris or Myrrh for instance) and we do not want to start with a too low plant/water ratio or we do not want to add water in the system during the distillation.
- We want to maximize the essential yield (it can have a positive impact on the essential oil yield if it does not separate easily from the hydrolat or if it contains a large proportion of oxygenated compounds).
- We want a more complete essential oil (if we do not produce hydrolat, more water soluble compounds might end up in the essential oil).

Note that we can also gather the hydrolat for 1 or 2 hours of the distillation and then keep distilling with cohobation until we get all the essential oil.
How long should I distill?
One of the most common questions which cannot be answered alone as it depends on other parameters such as the steam flow.

However, we can still say that plants which mainly contain monoterpenes and their derivatives in superficial glands (trichomes) on flowers and leaves are usually distilled pretty quickly. This is for example the case for lavender which can be steam distilled in about 1 hour with a proper steam flow (more information about the steam flow below).

On the other hand, if the plant contains a large proportion of sesquiterpenes and their derivatives (less volatile that monoterpenes) and/or if the volatile compounds are enclosed in hard tissues (wood, roots, rhizomes...), the distillation can be much longer. This is for example the case of vetiver which takes more than 24 h to be distilled at normal pressure.

If a plant contains quite volatile components in internal structures (like conifers which contain volatile components in resin ducts), comminution helps but it still needs to be distilled for a few hours (4-5 hours for most conifers) because an important part of these volatile components has to diffuse through the plant tissue to be distilled and this takes time.

In any cases, what we recommend when you start working on a plant is to draw a distillation kinetic which is a graph where you plot the cumulative yield (y) against the distillation time (x). You will see that the yield stabilizes after a certain time. If it does not, keep distilling to get a complete essential oil. This type of graph is a great tool that helps to decide when you can stop a distillation, but keep in mind that even the minute amount of essential oil you get at the end of the distillation can have a significant impact on its composition thus quality.
What is the ideal distillation flow?
Whether you perform a steam distillation or a water distillation, one important parameter in plant distillation is the steam flow. Again, the ideal distillation flow can be pretty different from one plant to another, but we can still give a few guidelines.

If the plant contains its volatile components in external structures (=trichomes), they are almost directly available for distillation. They only need to be freed from the trichome sacks which happens quickly as steam rises through le plant material. In this case, it is advisable to use a good steam flow to quickly carry them to the condenser so that they do not stay too long at 100° C. Now what is a good distillation flow? We usually consider in the field that 10% of the still volume per hour (100 kg of steam per hour in a 1000 L still) is a good steam flow. Tim Denny (2001) who published an extensive work about herbaceous plants distillation states that the steam flow should be calculate as a function of the cross-section area of the still and that a good flow rate should be between 2 and 4 L/m2/min. For a production still around 1500-2000 L, these two ways to express a good distillation flow (10% of the still volume per hour or 2 to 4 L/m2/min) are similar.

On the other side, if you distill conifer branches/needles, sliced rhizomes, wood chips or any aromatic material containing the volatile components inside the plant tissues, the limiting factor is the diffusion of these volatile components out of the plant tissues. Thus, distilling at the speed mentioned above is not advised as it would be waste of energy. In such cases, an ideal steam flow could be around 1/2 or 1/3 of the one mentioned above.

In all cases, it is important to understand that the ideal steam flow for a given plant material depends on many other parameters such as the comminution (particle sizes), the compaction of the plant material, the insulation (or not) of the still, the width and height of the plant charge, etc... Thus, it cannot be determined alone, without any consideration for the other distillation parameters. Also, what is ideal for the EO yield may not be ideal for its quality, the spent energy, the distillation speed, etc… and reciprocally. What I recommend is first to clearly set the priorities (quality > yield > distillation speed > spent energy for example but it could be different), then perform at least 3-4 tests for a given plant with a given still at different steam flow (all other parameters being unchanged) and see what gives the best results for your priorities.
What is the best time to harvest an aromatic plant material?
Coming soon
Should I dry or wilt my plant material before distillation?
Coming soon
Should I distill with agitation?
Coming soon
What is turbodistillation?
Coming soon
What is the ideal steam flow for my distillation?
Coming soon
Should I distill under pressure or under vacuum?
Coming soon
At which temperature should I distill?
Coming soon
What is the ideal temperature for the distillate?
Coming soon
How can I efficiently separate my essential oil from my hydrolat?
Coming soon
How can I know if my distillation is finished or not?
Coming soon
What should I do with the essential oil after the distillation?
Coming soon
My essential oil has a weird smell after the distillation, is it normal and what can I do?
Coming soon
Hydrolat or hydrosol?
coming soon
Is it different to distill for the essential oil or for the hydrolat?
Coming soon
What can I do with my distilled plant material?
Coming soon
How should I clean my still after my distillation?
Coming soon


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