distillery unit

How spirits are made – Visiting the Koval distillery

What is better marketing than inviting some interested customers to your facilities, touring them around, giving them a few tasters and telling them all about your company? It my experience, it works great (at least on us it does). Touring a food/drink company is a lot of fun and a lot of people seem to be tempted at the end to buy something or at least tell their friends & family about it.

We’d been to several of these tours at breweries (why don’t food producers do this as much?!), and now had to chance to go visit a distillery, Koval. Of course, we soaked up information on how their production process and distilling actually works, to share with all of you.

What are spirits?

At Koval they make spirits which are distinctly different from other alcoholic drinks such as beer, cider and wine. These are all alcoholic drinks with a quite aoderate alcohol content. Normally, they’re well below 10v% alcohol (although a few exceptions exist). Spirits on the other hand are characterized by their significantly higher alcohol content, being higher than 20% and often going up to 40%.

Beer and wine are made by fermentation of sugars into alcohol using yeasts. Whereas spirits start out the same way, they have to undergo a second process step: distillation. The yeasts aren’t able to continue to ferment under the high alcohol conditions of the spirits. It’s this distillation process that makes spirits unique and enables their high alcohol contents.

How spirits (gin, whisky, bourbon,…) are made at Koval

Spirits can be made with just one ingredient (and some yeast). This one ingredient is often a grain (rye, wheat or barley for instance), but can also be fruit or a starchy product such as a potato. Of course, you can also mix them, to create different flavours.

Here we’ll assume we start with a grain but the process is pretty much the same for the other types of starting materials. Also, we’ll describe the process as it’s used at Koval for making their rye whisky. For other manufacturers are drinks it will be slightly different, but the core principles remain the same!

Preparing the grains

We start with grains, rye in this case. The grain is milled in a hammer mill before being placed in a mash tank. During milling the grains are broken down into smaller particles which will make the nutrients in the grain more easily accessible for the next steps.

What was interesting to hear is that nowadays they don’t necessarily malt the grains anymore for these spirits. This process (which is also used for beer) breaks down the starches into sugars so the yeasts can convert these into alcohol in the next step. A disadvantage of this process though is that the flavour profiles of the grains change quite a bit.

Nowadays, we’ve figured out what causes the breaking down of the starch during malting: it’s done by an enzyme called alpha-amylase. Since we are now able to actually make alpha-amylase (bakers use a slightly different enzyme in bread as well). So, instead of having to malt the grains, we can add the enzyme directly to the grains to do its job in as little as 24 hours (as opposed to days). As a result, you’re left with more of the original grain flavour (which in the case of Koval is exactly what they want).

Fermentation – from sugars to alcohol

Now that the sugars of the grains are readily available the grains are moved to a fermentation tank. Here, yeast is added and the yeast will start fermenting the sugars into alcohol.

Whereas this process step can easily take a few weeks for beer, it only takes 6-8 days approximately for these spirits. This is because a slightly different type of yeast is used, what we call distillers’ yeast. This yeast is tuned towards the fermentation of spirits mixtures. Since this fermented mixture will still be distilled in a next step, you’re looking for slightly different characteristics than you would be in a beer.

In general, the type of yeast you use in this step strongly influences the final result of your spirit. Some yeasts will wash away any trace of the original flavours of the grains whereas others manage to conserve those better. The choice of yeast here depends on what final drink characteristics you’re looking for.

distillery unit
The formerly used distillation unit, this is now just used for tours and process explanations.

Distilling to make spirits

Until this point, the process for making spirits has been very similar as it is for beer. However, here it starts to deviate with the next step being distillation.

Yeasts cannot survive and thrive when there is too much alcohol. Therefore, if you want to create drinks with an alcohol content above 20% you need to find another way to increase the alcohol content further. The most common process to do this is distillation.

In the distilling process you use heat to separate two liquids (in this case alcohol & water). Since alcohol has a lower boiling point than water is evaporates more easily than water. You can use this to increase the alcohol content through several steps of distillation. Along the way a lot of the desirable flavour molecules get transported along and will end up in the final distillate as well. (We’ve discussed distillation in more detail elsewhere.)

Out of the distillation unit come three fractions, all of them are completely transparent and look like water (but they’re not!). Only after the next steps will they get their characteristic colour:

  1. The head: this first part that comes out of the distillation process is actually poisonous since it contains methanol. Methanol has an even lower boiling point than alcohol (ethanol) and thus comes out in this fist part. You should not drink the head. It makes up about 10% of the distillate.
  2. The hearts: this is the most flavourful part of the distillate. It is what you definitely want to use for your drink. At this point you can drink it, but it is still quite sharp, not as refined a spirit.
  3. The tails: this last part contains a lot more undesirable flavours and molecules. You can use this part but especially higher quality distilleries will not.
distillate portions
The three fractions coming out of the distillation process, they look identical, but have a very different chemical composition!


Almost all spirits go through some form of aging. This step is what gives colour to the drink and it changes and enhances the flavour considerably. This aging is generally done in wooden barrels, often made out of oak. The type of barrel, the time it is in the barrel, whether it’s a new or previously used barrel will all impact the flavour and colour of your final drink.

There is a lot of legislation to distinguish between different spirits. These will generally give requirements for this aging process. For example, some need to be aged for a minimum number of years or may only be aged in a specific type of wood (Scotch for instance).

We’ve discussed the aging process in way more detail before. An interesting fact that we learned during the Koval tour is that most of the oak barrels they use aren’t made from fresh pristine oak. Instead, after the barrels are made they are charred on the inside. The wood will turn black and a lot of flavour molecules are formed during this process. By then aging the spirits in these barrels their flavour becomes way more complex than it ever would in a ‘clean’ one! (This article has an amazing photo of the blackening process.)

Aging takes time, but for how long still?

Conventional aging in barrels takes time. At Koval aging for 3-4 years is very common but there are a lot of spirits, such as whiskys, that are aged for decades before being bottled.

For a long time it hadn’t been clear what really happens during barrel aging. However, nowadays we know better and better what happens and as a result a machine has been invented to speed up this aging process to a matter of days and weeks instead of years! The technology is used by Lost Spirits distillery and was extensively discussed in a Gastropod podcast episode (Oct-2018).

It is a fascinating technology and you might be wondering why not everyone is using it already. Well, for now using the technology is about the same price as using the conventional barrel aging technology. Of course, that may (and likely will) change with time. For now, it is a good competitor and is actually ideal for doing research & development. Instead of having to wait at least 5 years before knowing whether your whisky turned out good, you can now try it in a matter of days!

Koval distillery

Of course, our Koval guide did not forego the opportunity to tell us more about the history of the distillery. It is actually still quite a young distillery, they started up in 2008. At the time they were the first distillery to open up within the city of Chicago limits since some time in the mid-1800s. Due to the prohibition (a time in the early 20th century in which alcohol was forbidden throughout the US) and various other circumstances, it had never happened before.

That ended our tour through the Koval distillery, but of course, not before we tasted some more of their drinks. We learned that they make mostly whiskies. Some of them are made from just one grain, whereas others are made from a mixture of grains. It is surprising to see how these grain differences result in such large differences in drink flavour!

3 single grain whiskies
From left to right: three single grain whiskies, millet, oat and wheat. All these whiskies are also ‘single barrel’. This refers to the fact that different barrels haven’t been mixed together at the end to create a consistent flavour. Instead, there will always be slight differences between batches from individual barrels!

That brought the tour to an end. And, to confirm that this type of marketing does magic, we did indeed buy a bottle of whisky, a cranberry flavoured one…


Want to learn more about Koval? Visit their website.

Clawhammer supply, The best yeasts for distilling, link; a great example of how different yeasts can result in a very different drink

Gastropod, Espresso and whisky: the place of time in food, Oct-2018, link

Katzen, R., et al., Ethanol distillation: the fundamentals, chapter 18, link; for those who would really like to understand ethanol/water distillation

Vinepair, What are spirits?, link

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