Basics of Distillation & Different Distilling Processes

Distillation is used for numerous applications, including the distillation of essential oils and spirits. Our Copper Alembics are perfectly suitable for these applications nevertheless certain precautions should be taken to avoid personal injury as a result of negligence or the continuous consumption of poor results.

Distillation is a basic chemical science which involves the separation of a chemical substance into its different components based on difference in the boiling point of each fraction. This is done by heating a mixture in an alembic pot so the fractions that make up the mixture begin to evaporate, these are conducted via a connecting arm or swan neck into a condenser where they are chilled and revert to their liquid state.


Simple (Water) Distillation

Alembic stills employ simple distillation methods. They are made up of a copper pot often referred to as a boiler that is connected to a cooling recipient by means of copper piping known as a swan neck. The material to be distilled is inserted into the boiler along with water. The pot is then fired by wood, gas or coal. The distiller has very good control over the pot still temperature and can regulate the strength of the distillate to fit his objectives.

By way of example when boiling water we have often observed how the steam from a kettle condenses back to water when it comes in contact with a cold surface. This simple technique is applied to the separation of a mixture into its different parts by boiling the mix in a boiler, condensing the vapors and collecting the resultant liquid.

The process begins by heating a fermented mash or wash, in the boiler of a pot still or alembic. As the temperature rises the most volatile constituents of the mixture (those that vaporize at lower temperatures) begin to evaporate first. This will permit us to isolate the different components of the mixture as these will dominate at different temperatures. By taking accurate temperature readings one can ascertain which component is dominating at that temperature. As the vapors accumulate in the head of the alembic they find their way to the condensing recipient via a connecting tube or swan neck. In the case of the traditional alembic the swan neck tubing leads to a serpentine coil in the condenser filled with running cold water. Once the vapors come into contact with the cold surface of the serpentine coil they condense to their liquid state and trickle down to where they are collected, in an appropriate vessel drop by drop. This process has to be carefully monitored so you know exactly what you are collecting at any given stage of the distillation as we do not want to be collecting any harmful substances.

Most distillation methods are based on the simple distillation method with some modifications. Simple distillation is quite adequate for isolating fractions from a wide variety of substances with different boiling points and may be used for distilling seawater into pure water, for example. Obviously its main application is for the distillation of alcoholic spirits from any number of fermented substances in which alcohol is present. It may seem obvious to say that, but to clear up any apparent misconception it must be stated once again that what we are doing here is not making something new which was not there to begin with but simply separating the alcohol from the mix. So you will end up with the same amount alcohol but more highly concentrated.

Ethanol alcohol evaporates at 78.3ºC at sea level and water at 100ºC but a mixture of the two components will evaporate between 78.3ºC and 100ºC depending on the ratio of ethanol alcohol and water. The more volatile components or those fractions with a lower boiling point will tend to evaporate first so the resultant vapors will be more enriched with those components with a lower boiling point. A fermented batch may be composed of ethanol, other higher alcohols such as methanol also acetone, various esters, water and furfurals. The more volatile components such as acetone, methanol and the various esters are undesirable; methanol for instance has been known to cause blindness. It is common practice to throw away the first portion of the distillate, this way you will get rid of the methanol. Separate and discard the first 50ml if distilling a 25 L wash or mash in a reflux still or 100ml per 20L wash from the rest of the distillate if using a traditional alembic, these fractions are known as fore shots or heads and are distilled first.

The result of any distillation is divided into three separate parts in the following order: heads, hearts and tails. The best and desired portion of the distillation is obtained from the hearts. Cut off points have to be determined between heads, hearts and tails, the art lies in when to start collecting the hearts and when to stop. Experienced distillers use their senses to determine cut off points, they monitor the taste and smell of the heads, these usually have a very sharp taste and are foul smelling. The hearts portion of the distillate (the ethanol) should be totally transparent and odorless. The tails contain a large amount of compounds with higher boiling points, such as the higher alcohols and furfural. These compounds can spoil the taste of the spirit if the collection is carried on too long. The cut off point for the tails can be identified by the taste, smell and milky cloudiness of the distillate. This is done by collecting a few drops on the back of a spoon every so often and checking what it tastes or looks like on a regular basis. The tails are usually saved to include in the next batch as a considerable amount of ethanol alcohol can still be recovered.

Cut off points may also be established based on temperature or alcoholmeter readings. Temperature readings may not determine the cut off point with the greatest accuracy though they may be helpful in determining the end of a complete distillation run. For instance when the vapor temperature nears 98°C most of the alcohol has already been distilled and it becomes unnecessary to continue the distillation process. The percentage at which to do the cut may depend on the flavor profile you may want to obtain and the kind of wash distilled. As a rule for fruit mashes the cut off point for tails may be 25% alcohol and for grain washes 18%, this is not a hard and fast rule and the distiller has to toggle with these values to obtain the desired flavor profile. Most distillates are double distilled to further purify the distillation results and raise the alcohol percentage. A second distillation may also concentrate the flavor further. The cut off point for a second distillation in a fruit mash may be as low as 60%. For grain washes a cut off point may be established at 58% or higher.

Alembic stills yield better taste and more characteristic distillates but are slow and require more labour. Nonetheless single malt Scotch whiskey producers, a few rum manufacturers and other quality oriented distillers employ pot stills. In the U.S.A. more and more small distilleries are using alembic stills to produce high end products that are appreciated for their subtle refined taste.

Steam Distillation

As suggested by its actual name uses steam to distill instead of water and steam. This system is easily controlled and it is the distillation process required to obtain better quality essential oils and hydrosols. Steam distillation is carried out in a still. Fresh or sometimes dried botanical material is placed in the plant chamber of the still and pressurized steam is generated in a separate chamber and passed through the organic material to remove the oils.

Steam distillation is a technique employed to distill alcohol or extract essential oils from organics by passing steam generated in a pot still through the plant material. Temperature sensitive compounds which would normally decompose through simple distillation vaporize at lower temperatures when subjected to steam in the vapor chamber or column of the still. This allows for the separation of essential oils, which tend to be less soluble in boiling water, from chemically complex materials. When the steam passes through the organic material tiny pockets that hold the essential oils open to release the essential oil molecules without damaging or burning these delicate components. The distillate will contain a mix of water vapor and essential oils which return to their liquid form in the condensing recipient and are separated using a Florentine separator (Essencier) or separating funnel. Both the essential oils and the water called floral water or hydrolats is retained. The distillation procedure is the same as for the simple distillation method with the exception that distillation takes place by means of steam.

As for essential oils, using steam for alcohol distillation permits the distillate to retain the more delicate flavors and aromas which would otherwise breakdown if subjected to high temperatures. This process is typically used to extract essential oils from aromatic plants to flavor liqueurs. Alternatively alcohol may be distilled from fermented matter placed in the column of an alembic such as pressed grape skins left over from wine making.

There are obvious advantages to steam distillation with commercial applications in the food, medical and chemical industry, for example aromatic oils, hydrolats, perfumes, essences and flavored liqueurs.