Distilling Terms and Jargon Explained (Learn These!)

If you are new to the world of distillation, you may have noticed a bunch of distilling terms and terminology being thrown around that you are unfamiliar with.

Distilling, like many other industries, has its own jargon and special terms, and no one ever explains these to you at the beginning!

In this article, we will decipher some of the most common words and terms used in the world of distillation. 

Compounds

During distillation, a liquid mixture is separated into its component parts through condensation or vaporization. The purpose of distillation is to purify the liquid. This is achieved by separating a compound from volatile and less-volatile material by heating the liquid. Different compounds in a mixture may have different boiling points by which separation can be achieved. For example, alcohol has a lower boiling point than water. When the mixture is heated up using a heating source, the alcohol will start to evaporate first. It will turn into steam and rise up the still. The alcohol vapors are collected and cooled down to form liquid again, after which the purified liquid is collected. There are different types of compounds.

Azeotrope

You may be wondering: what is an Azeotrope? Azeotrope is often referred to as a constant boiling point mixture due to the fact that it has a constant or near constant boiling point. It is a mixture that consists of two or more components. Azeotrope consists of 95% ethanol and 5% water. What is important for distillers to understand is that ethanol boils at 173.12 °F (78.4 °C) and water boils at 212 °F (100 °C). But, Azeotrope boils at 172.76 °F (78.2 °C). This means that Azeotrope boils at a lower point than both of its constituents. Because the boiling point of Azeotrope is below the boiling point of pure ethanol, the ethanol cannot be extracted by simple distillation. A special type of distillation needs to be used to separate the components, known as azeotropic distillation. In order to purify the liquid, the Azeotrope must be broken first. This will involve a separation technique that is not dependent on simple distillation.  A separation agent is added to the mixture. Toluene is one of the most popular separation agents used in this process. Another popular method used to remove the last remnants after separation are molecular sieves. The sieve absorbs the water from the mixture and is a great way of obtaining absolute ethanol. 

Ethyl Acetate

Ethyl acetate is a compound that occurs naturally in some fruits such as apricots, bananas, grapes, berries, melon, papaya, etc. It is responsible for the sweet aromas and tastes of these fruits. It is also found in some grains such as wheat and rye. This compound can also be produced synthetically by reacting two different compounds with each other: acetic acid and ethanol. In addition, this compound is the most common ester produced in wines. Certain types of yeast are more prone to producing ethyl acetate during the fermentation process than other types of yeast. You’ll find that ethyl acetate is produced by yeast during the fermentation process in the production of wine.  At lower levels, the presence of ethyl acetate in wine is a good thing. It will produce a fruity flavor and a sweet aroma to the wine. However, on the bad side, ethyl acetate has been associated with wine spoilage for a very long time. It is also one of the most common esters found in whiskey and is an indication of maturity in alcohol. 

Esters

It is an organic compound that is responsible for the flavor and aroma found in some alcoholic beverages. Most notably, esters impart a sweet and fruity taste, most commonly found in certain wines, rums, whiskeys, and brandies, into the alcohol. It is derived from an acid where at least one –OH hydroxyl group is replaced by another –O– alkyl (alkoxy) group. In more simple terms, an ester is a molecule of alcohol that is mixed or fused with a Carboxylic acid. Esters are typically formed during the distillation process, more specifically, during condensation reaction between alcohol and carboxylic acid. Let me explain this. During a condensation reaction, two molecules will join each other to create a larger molecule while at the same time eliminating smaller molecules. In certain cases, the production of ester may need to be controlled. This can be achieved through careful selection of the yeast that is used during fermentation. As certain types of yeast are known to produce higher levels of ester. In addition, the temperature during fermentation may contribute to higher levels of ester being formed. Therefore, it is important to control the temperature during the fermentation process in order to slow down the production of ester. 

Methanol

Fermentaion produces an unwanted by-product: methanol. It is one part carbon, one part oxygen, and four parts hydrogen. Natural yeast is responsible for the production of methanol during fermentation when pectin, which naturally occurs in the wort, is hydrolyzed. It produces sufficient amounts to be extremely dangerous or even fatal when it is present in the final product. During distillation, methanol is vaporized first as it has a lower boiling point than ethanol. The size of the batch will also affect the amount of methanol that is produced. The production of methanol can be controlled. Fruits that are high in pectin should not be fermented. In addition, use healthy yeast and control the temperature during fermentation. Keep in mind, that if distillation is performed incorrectly, methanol will still be present in concentrated amounts. During distillation the heads and fores should be removed. These are the first parts of the run during distillation. 

Fusel Alcohol

The word fusel means “bad liquor” in German. Fusel alcohol is also known as fusel oil. Fusel alcohol, a mixture of higher alcohols, is caused by strenuous fermentation and high ethanol concentrations during the distillation process. It is a by-product of ethanol fermentation. Higher alcohol levels contain two carbon atoms. Certain fermentation conditions such as temperature, aeration, and nitrogen promote cell growth, and may create higher levels of fusel alcohol. At the end of the distillation run, concentrated amounts of fusel alcohol can be found in the tails. A reflux still can separate these concentrated amounts of alcohol. 

Turpenes

Turpenes are organic compounds that are produced by certain plants, such as coniferous plants. They are responsible for giving certain plants their smell and aroma, such as the pine smell in coniferous trees. Turpenes are also one of the aroma compounds found in many wines. This specific group of compounds is often responsible for specific flavors and notes found in certain types of alcohol, such as rose, floral, pine, citrus, and mint. Wine is made of grapes and all grapes have turpene. Some grapes have them in very high quantities while other grape types have them in much lower quantities. Terpenes are also present in the agave plant, which is used to make different types of alcohol, such as tequila. 

Fractions

Cuts are points in the distillation run where the distiller will separate the run or distillate into smaller fractions. In essence, cuts and fractions are terms that are used interchangeably to discuss the cut points and sections in the distill run. In the distillation process, alcohol is divided into three fractions or sections; the head, the second fraction, and the tail. The head predominantly contains compounds that have a low boiling point. The second fraction, which is also known as the heart, is the primary or main product of distillation, and the tail, which has much lower amounts of alcohol in it. Distillers who seek to make good cuts in the distillation run must understand the difference between cuts and fractions as well as being able to identify the different fractions, in order to make proper cuts in the run. 

Foreshots are the first fraction in the distill run. One of the major components of foreshots is acetone. The second fraction is known as the head and some of the major components in the head are ethanol, ethyl acetate, acetone, and methanol. The next fraction is the heart. This is the purest section in the run. The hearts have a very clean smell and taste. It is the purest form of ethanol in the entire run.  The final fraction is the tail. The tail of the run is known for its unpleasant smell, including wet dog or wet rag. This is the section of the run where you will find the fusel oils. These fusel oils infuse your final product with an unwanted flavor and aroma. 

Congeners

Congeners are produced during the distillation and fermentation processes. These minor compounds occur naturally in alcohol and alcoholic beverages. Essentially, congeners are a by-product of the fermentation process. The level of congeners present in the alcohol will depend on the type of sugar that was used to produce the alcohol. It is believed that congeners affect the taste, flavor, and aroma of certain alcoholic beverages. There are a few examples of congeners produced during the distillation process:

• Esters
• Ketones
• Acids
• Sweet smelling alcohol
• Aldehydes

While the amount may vary from one alcoholic beverage to another, the more distilled a spirit is the lower the amount of congeners are present in the alcohol. 

Heads, Hearts and Tails

Heads, hearts, and tails refer to the different sections of the distillation run. After the foreshots, the heads are the initial part of the run. The distiller will make several cuts in the run to distinguish between these sections, which are known as the fractions in the run. The heads of the run are known to produce a sharper taste similar to a bite. This section has a distinctive sweet and buttery smell to it. The heart of the run is the main part and the purest part of the run. The major compound produced in the heart of the run is clean ethanol. The heart does not have the chemical bite found typically in foreshots or in the head of the run. The final part of the run is also known as the tail. This is the undesired part of the run that has a distinctly bad odor, much lower levels of alcohol, and much more fusel oils.

Phenols

Phonols is a compound that produces certain flavors in alcohol during distillation such as clove-like, smokey, medicinal. In some distillation processes it is welcomed, while in others it is completely undesirable. This will depend on what the distiller is aiming to achieve. Phenol compounds contain hydroxyl (OH) and hydrogen and carbon molecules. 

Distilling Terms

Smearing

Smearing is where different fractions mix together and is usually undesired. For example, you would want to completely separate your heads and hearts fraction but in reality they will smear together.

Smearing is greater on a pot still than a reflux still.

Smearing can also be used to describe flavors.

Bleeding Off

Bleeding off describes carefully and slowly taking product from the still. For example, you would slowly bleed off the foreshots from your reflux column to avoid disturbing the equalisiation of the column

Distillation Columns

Distillation columns are also known as distillation towers. These columns are made up of several components. Each part of the distillation column is used to either enhance material transfer or  to transfer heat energy. 

Vapour Management

This specific type of column is a relatively new design. Vapor is separated into two streams. Each stream is then condensated separately. The vapor is separated before reflux is generated, which results in a 1:1 reflux ratio. The finished product collected out of the column is not in liquid form but in vapor. A high level of purity can be maintained through this system. Vapor rises up the column towards the reflux condenser which pushes the vapor back down to be distilled even more. There is a product valve installed at the head of the column. This valve is used to remove a small portion of the vapor. The vapor is then pushed towards the product condenser which is collected as a finished product. 

Cooling Management

The cooling management design is a very common design. The column is cooled down before the product takes off. Vapor is sent by the column riser towards the reflux condenser. The condenser then performs one of two functions based on the controlled flow of cooling media. A portion of the vapor will be recondensed while the remaining portion will be routed toward the product condenser. A valve manages the cooking media and the flow rate. A cooling management system directly influences the ABV/proof of the distilled product. 

Bokakob

The Bokakob was designed in 2001 by a man named Alex Bokakob. It is a dual-slant, single column, in-line, reflux still. It was originally designed to sit on top of a stovetop boiler. There have been several major changes made to the design over the years. It is a very simple and basic distillation tool. It is very popular amongst those that are new to distilling due to the fact that it is very simple to use and has an easy to understand design and is able to produce 95% ABV. The original design was built with a 1.5 inch column. It is made from copper or stainless steel. 

Liquid Management 

Alcoholic vapor is pushed up the column riser using pressure. When the vapor makes contact with the reflux condenser it is recondensed to liquid form. The liquid then falls back down the column riser where it is revaporized. A small portion of the liquid in the column is captured in a cup/slant. During the distillation run, this liquid is slowly drained out. The overflow from the cup is redistilled. Both the overflow and the reflux create a much purer liquid. 

Pot Still

A pot still is a type of distillation apparatus. This type of still is predominantly used to distill flavored liquors such as Irish grain whiskey or cotch malt whiskey.The mash is contained in the pot. A fire is used to heat the pot still directly. These stills are predominately made of copper due to the fact that direct heat is applied to heat the mash inside the pot. These stills are very popular in the production of spriters that have pronounced flavor. Pot stills are used in batch distillation. 

Plate Still

These stills have columns with plates inside of them. The purpose of the plates is to help redistill the liquid in order to create a higher proof. The vapor inside the column comes into contact with the plates and caps. This results in the vapor being condensed back into liquid. The vapor rises then condenses and cools, causing some vapor to move on and some of the vapor to drip back down the column. The liquid that falls will eventually be pushed back up the column. 

Bubble Plates 

Bubble plates essentially create more reflux in the column. This ensures several distillation cycles in a single run. This means that the liquid will change to vapor and back to liquid several times in a single run until a purified alcohol liquid is created. The bubble cap is the main factor responsible for this cycle, known as phase change. 

Thumper

The thumper keg is a very old design. It is often referred to as the doubler. It can speed up the distillation process and increase the alcohol content of certain wines and spirits. Vapor from the head of the kettle is moved along a tube to the bottom of the thumper. When the vapor enters the thumper it is cooled back down to a liquid. The vapor is condensed while the liquid in the thumper is heated at the same time. Thumper kegs are traditionally made of steel, wood, or copper. 

Reflux

Reflux stills are some of the most common and popular designs of stills used today. Reflux still creates alcohol with little to no flavor as well as substantially higher proof. The still has a fractioning column inside it. The rising vapor is condensed through the help of liquid reflux. This helps to increase the efficiency of the distillation process. And, in turn, the purity of the liquid is intensified. 

Shotgun Condensor

A shotgun condensor is a cooling apparatus. It cools vapor down and transforms it back into liquid. The shotgun condensor is attached to the top of a packed column. It has a plate installed in it. This plate helps to divert a portion of the condensed alcohol. The condensed alcohol is diverted out of the collection tube. The remaining liquid will drop over the packing.                                    This type of condenser is used in a reflux still design. 

Dephlegmator 

A dephlegmator is a column made with plates or column packing that will either partially or fully condense vapor that travels through it. Condensation is created at the top of the column. It is known for creating layers of condensation through this process. Liquid that has a higher boiling point will return to liquid form while liquid that has a lower boiling point will remain vapor and pass through the apparatus.The main function of a dephlegmator in distillation is to produce liquid for reboiling.