WHISKY STILLS

As the whisky industry evolves, so does the art of making whisky. Most times, the changes are subtle, but occasionally an innovation comes along that sets the industry on its head. Perhaps nowhere is this more evident than in the development of the still.

Evidence exists that cultures as far back as 3000 B.C were practicing some form of distillation. During this early period, the distillation process focused on distilling herbs for aromatic oils and medicinal potions. We also know that as early as 500 B.C. Britians were making “mead,” an alcoholic product derived from honey.

ILLUSTRATION OF AN ALEMBIC STILL

Alembic Still

Alchemy

Distillation also played a vital role in the practice of alchemy. For the most part, alchemists relied on the use of an alembic still, which consists of three parts: the “cucurbit,” a vessel containing the liquid to be distilled.  The second component is the “head” or “cap,” a dome-shaped structure that fits over the mouth of the cucurbit. The head has a downward sloping tube attached that leads condensed liquid to the final component, the “receiver,” which is a container for collecting the distilled liquid.

Over time alchemy evolved into chemistry, and distillers were creating a more extensive range of products, modifying the alembic still to suit their needs. In Italy, for example, we know that Christian monks were concocting a brandy-like drink in the 1300s, and Russians were making vodka in the 1400s.

Whisky Distillation

Historians believe European monks introduced the practice of distillation to Ireland in the 1400s. There, attention shifted toward cereal crops such as barley and rye, and the Celts began making “uisce beatha” or water of life. It was during this period that a modification of the alembic still evolved into what has become the iconic onion-shaped copper still we associate with traditional whisky-making, the copper “pot still.”

The pot still would dominate the whisky industry for another 400 years until in the early 1800s when the introduction of the column still radically changed the process of making whisky. And innovative approaches to distillation continue to impact the whisky industry. Modern Hybrid Stills provide distillers with greater flexibility, resulting in a wider range of whisky types.

POT STILL

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The copper, onion-shaped pot still evolved from the alembic still used by ancient cultures. In concept, it has changed very little. Like the alembic still it consists of three basic elements. A pot, a neck, and a long arm that collects and transfers vapor to a container. But that is not to say the pot still has not evolved or that it is not continuing to evolve.

The original alembic stills were most likely ceramic. As the use of the alembic still spread across the world, cultures adapted the design relying on local materials and tradespeople. There were three essential requirements for the construction of a still. First it must be water and airtight to allow a solution to reach a boiling point and vaporize. For optimal results the still must be able to conduct heat uniformly. And third, it has to be built in a manner that allows the vaporized solution to condense and collect in some type of vessel.

Through trial and error, the iconic pot still emerged. Early variations were used to make brandy in Italy, Cognac in France, Vodka in Russia, and Gin in Britain. It was the Celts; however, that perfected the iconic pot still design in the late 1400s, early 1500s.

Metals replaced ceramics, and through trial and error, it was decided that copper was the ideal material because it was easily malleable and uniformly and efficiently conducted heat. By the 1800s, the pot still was the primary type of still used in making Irish and Scotch whiskies.

Pot stills come in various sizes and shapes. While the design and configuration are subjective, there are several common denominators. First are the components. Each pot still will consist of a pot, a neck, a Lyne arm, and a condenser.

However, some designs might include modifications such as a “reflux bulge,” which increases the surface contact between the vaporized alcohol and copper siding, causing heavier alcohols to condense and return to the solution.

Proportions also vary a great deal, as does the length and configuration of the neck. Tall necks allow for more surface contact increasing the amount of reflux produced. Consequently, tall, lean necks tend to yield lighter, fruiter, more delicate whiskies. While shorter, thicker necks produce waxy, heavier, oily cereal flavored spirit. The Lyne arm determines how quickly vapors liquify and also vary a great deal in length, diameter, and angle.

Another design variable is the material or materials manufacturers use to build the pot still. Copper is the traditional material for several reasons. First, it is easily malleable. Second, it is an excellent conductor of heat, enabling the distiller to achieve a unified temperature in the pot. But its most attractive feature is that copper reacts on a molecular level with sulfur compounds created during fermentation. In effect, it removes these compounds from the wash, canceling out the bitter sulfur taste that would otherwise be present.

But copper does wear out and needs periodic replacement. This drawback is costly forcing distillers to explore alternate designs. Some newer pot stills are made of stainless steel, often incorporated with a copper alloy. Copper is also used in the design of other components such as the condensers to trap sulphuric compounds that a stainless steel pot might not capture.

Distilling whisky in a pot still is a relatively straight forward process. In the first stage, the distiller adds fermented wash (≈ 8% ABV) to the wash still. She/he then heats the solution, and at 100° C the alcohols begin to vaporize and collect in the Lyne arm. This solution has a higher alcohol content (≈ 25% ABV) but contains harmful alcohol and distasteful congeners.

Heads, Hearts, and Tails

The distiller then adds the solution to the spirit still, where the process repeats. This time, however, he/she separates the collected spirit into four fractions. The first part is called the “foreshots.” Foreshots account for less than 1% and begin to accumulate at 50° C and consist mostly of acetone. Acetone ((CH3)2CO) is a colorless, volatile, and flammable liquid. It is extremely poisonous and is discarded.

The next fraction collected is the “heads,” approximately 3% of the solution. Heads are a mixture of acetone, methanol, ethyl-acette, and ethanol. They have a slightly sweet smell and a solvent-like taste. While the heads contain less desirable elements, they are also rich in ethanol (C2H5OH) or potable alcohol. To maximize the collection of this desired alcohol the heads are collected and added to the next distillation run.  It is up to the distiller to determine when the heads begin and end.

The third part collected is termed the “hearts.” This portion contains the highest percentage of ethanol, which has a clean taste and lacks the bite commonly associated with the heads. The heads also contain esters and other congeners that contribute to taste and character. Hearts make up the bulk of the distillation run.

The last portion collected is the “feints” or “tails.” This portion contains various esters and congeners including “fusel oils.” Fusel oils, German for “bad liquor,” are longer chain alcohols, are mildly toxic, and have an unpleasant aroma and taste. However, in small concentrations, they give whisky added flavor and character. It is up to the distiller to determine the cut off point between the hearts and tails. The uncollected tails are often combined with the heads and added to the next distillation run.

COLUMN STILL

In the early 1800s, three men revolutionized whisky making by designing a new type of still.  The first of these men, Sir Anthony Perrier, operated the Glen distillery in Cork, Ireland. In 1822, he patented a new type of still that directed the wash flow through a series of partitions horizontally arranged over a heat source. One of the still’s drawbacks was that it required a considerable space to set up correctly. Another drawback was that it still required multiple distillations.

In 1828 a Scotsman named Robert Stein improved upon Perrier’s prototype. He designed a still that fed the wash vertically, through a column of partitions. He called it a “patent still” and he was able to install it in several distilleries. Unfortunately, Stein was unable to secure the financial support needed to perfect his still and enable it to gain industry acceptance.

However, his column still did catch the attention of Aeneas Coffey, an excise tax collector in Ireland. Coffey modified Stein’s design, inserting two pipes into the column that allowed for a portion of the vapors to recirculate inside the column instead of flowing into the receiver. This simple modification allowed for a continuous flow, eliminating the need for multiple distillations. In 1830 he patented his “column still,” setting the stage for a significant change in the way whisky was made but equally important, the way it was marketed.

Column stills can vary a great deal in height, circumference, and materials. The traditional Coffey Still is constructed of two vertical columns. Inside the columns, there are a series of perforated plates that vaporized alcohol rises through and a set of solid plates called spirit plates, which collect the liquidized spirit and send it to the spirit receiver.

The number of plates included in the column still varies according to the type of alcohol collected. Industrial column stills designed to produce highly volatile components used in solvents are often several stories high. These types of column stills yield alcohol as high as 96% ABV or almost pure alcohol. Whereas, American and UK laws stipulate that spirits used for whisky be less than 94.8% ABV.

Column stills used in making whisky are often stainless steel with perforated copper plates. However, some whisky column stills are entirely stainless steel and rely on other components in the system to strip the alcohol of sulphuric compounds.

The Coffey Still consists of two vertical components, the analyzer, and the rectifier. Cool wash enters approximately three-quarters of the way up the rectifier. The wash flows downward through a serpentine tube. The wash heats as it descends and exits near the bottom of the rectifier. It then flows upward through a pipe emptying into the top of the analyzer.

The analyzer consists of a series of perforated plates. Steam enters the bottom of the analyzer and rises through the plates. As it rises it converts the alcohol within the descending wash to vapor. The vapor collects at the top of the analyzer and returns to the bottom of the rectifier. The spent wash containing less than 1% alcohol exits through a pipe at the bottom of the analyzer.

In the rectifier, the vaporized alcohol rises through a series of perforated plates. And as the vapor rises it and comes into contact with the serpentine wash tube and begins to condense. Heavy alcohols and congeners liquefy and flow down to the bottom of the still, collected and returned to the top of the analyzer.

Lighter alcohols and congeners remain vaporized and continue to rise through the rectifier. Near the top of the rectifier the desirable alcohols eventually liquefy and collect on a solid plate called the spirit plate.  The collected spirit flows out of the rectifier and collects in the spirit receiver. The most volatile continue to rise and exit through the top of the rectifier.

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HYBRID STILL

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As the economy rebounded in the 1990s, consumers started treating themselves to luxury items. An item’s backstory began to outweigh price considerations.  Who made the product? What was the quality of the individual components? Did the product’s backstory reflect a cultural heritage? Was the story authentic? Was the manufacturing process sustainable? What impact did it have on the local economy?

The increased scrutiny disrupted traditional distribution channels enabling entrepreneurs to gain a foothold in broader markets. This anomaly was particularly evident in the beer industry. In 1990 there were less than 300 hundred craft breweries in the United States.  By 2015, that number rose to just under a thousand, but in the last five years, that number has exploded to over 7,000 craft breweries.

Craft distilleries experienced similar but not as drastic growth. In 2000 there were approximately 24 craft distilleries in the United States. By the end of 2018, that number grew to over 1,500. By 2020, that number will rise to over 2,000.

Distilleries have a high entry cost. For example, a traditional pot still can run between $75,000 – $100,000. Add to that the cost of the condenser, spirit safe, and other equipment, and you are looking at a significant investment. Moreover, if you are focusing on whisky, the maturation process means that any return on that investment might be years in the making.

So, craft distilleries looked for ways to offset the economic disadvantages. One way to do this was to distill a variety of products including vodka, brandy, gin, and various liquors. However, to do that, they needed more flexible equipment. Thus a need arose for a new type of still, the hybrid still.

A hybrid still combines components of the traditional pot still with elements of the upright column still. Manufacturers connect the two still types with piping, instruments, valves and other components. Hybrid stills vary a great deal in size and configuration. Some setups are comparable in scale to conventional stills, while producers design some to meet the needs of the microdistiller.

There are distinct differences between the way conventional stills (pot and column) and hybrid stills process alcohol. For instance, when making whisky in a hybrid still, the alcohol compounds separate from the mash in the pot, but they do not transfer to the condenser through a Lyne arm. Instead, they rise through a vertical, copper column containing a series of perforated plates. Only after passing through these plates does the vaporized alcohol reach the condenser.

If producing brandy, vodka, gin, or another spirit, the vaporized alcohol produced in the hybrid pot rises through one or more plated columns. In the case of vodka, it may pass through as many as three or four columns. Another distinguishing characteristic is that unlike conventional column stills that operate continuously, hybrid stills produce spirit in batches. Thus, another name for a hybrid still is a “small batch” column still.

Hybrid stills often contain elements that neither of the conventional stills typically use. An example is the dephlegmator located at the top of the plated column. The dephlegmator houses a series of small, plumbed tubes through which cold water passes. As the pressurized vapor comes into contact with the tubes a portion of the alcohol liquefies. It then returns to the bottom of the column. The balance passes on to the condenser.

Manufacturers construct hybrid stills from either copper, stainless steel, or a combination of both.

Hybrid stills rely on the same principles of processing alcohol as conventional stills but differ slightly in the step by step process.

When using a hybrid still the distiller often runs the mash through a vertical stripping column.  A stipping column resembles a typical plated column and consists of several plates designed to remove the solids from the mash.  The bulk of the stripping column might be stainless steel, but the plates and the upper portion of the column is often copper.

The mash then passes to the pot and heated. As in the conventional process, once the temperature reaches 100° C, the desirable alcohols begin to vaporize. The vaporized alcohol rise directly into a copper distillation column often referred to as a helmet. The vapors continue to rise through the distillation column and may encounter a series of copper plates.

hybrid still

The distiller can control the angle of the plates and thus influence the amount of reflux as well as the type of congeners captured. If a distiller desires light fruity alcohol, he or she adjusts the plates to create more reflux. But if they desire a heavier spirit they adjust the plates to almost vertical, allowing a greater percentage of heavier alcohols and fusel oils to pass to the condenser.

Dephlegmator

For even greater control, manufacturers install a dephlegmator at the top of the distillation column. By adjusting the flow of the water in the dephlegmator’s pipes, the distiller creates a closed system. The components found in the heads compress in the vapor phase near the top of the column, while the tails remain in the pot.

Controlling the flow within the dephlegmator enables the distiller to control the rate the hearts, which are located between the compressed heads and tails, leave the column. A skilled distiller can create a light, clear spirit with very clean hearts that require very little aging.

The flexible arrangement of the various components possible in a small batch, hybrid still enables a distiller to make a variety of spirits including vodka, gin, brandy and other liquors.