Filtering, Blending, Proofing,
and other Post-Distillation Techniques
Overview
While barrel maturation gets all the love and admiration, there are plenty of other post-distillation techniques that can have a massive impact on a spirit's profile. These can be employed for a variety of reasons including improving a spirit's taste, it's consistency from bottle to bottle, or simply it's marketability.
A producer can use these to make a few slight tweaks, or create something entirely new. Below is an overview of a handful of the most common post-distillation techniques. Details about how they are utilized across different categories are in each spirit's individual section.
Filtration
Many spirits are filtered to remove impurities to render a softer and cleaner spirit. Charcoal is the most common filter, particularly with vodka. Sometimes a spirit will be will be aged in a barrel to give it a richer flavor and then filtered to remove the color - this is common amongst many of the best white rums. Tennessee whiskey is famously filtered through sugar maple charcoal, aka the Lincoln Country Process, which imparts a mellowness that's lightly sweet.
Side note: though it has many tangible benefits, I think it’s fair to say that filtration's effect can sometimes be over-stated in marketing, particularly in the premium vodka market. A fancy, extensive filtration process won't make as big of a difference as is sometimes claimed.
Chill Filtration - Many barrel-aged spirits contain heavier compounds that are not soluble in water, which means if you put an ice cube into them they will become slightly cloudy. Chill filtration is a method that solves this problem. The spirit is chilled to freezing temperatures at which point these compounds can be filtered out.
This is done purely for aesthetic reasons, as cloudy booze doesn’t look as nice. Some whiskey purists disapprove of this practice because they say it sacrifices texture and flavor. From what I’ve tasted I think there may be something to that, but the jury is out. It should also be noted that if a spirit is above 46% ABV cloudiness will not appear, regardless of chill filtration. Regardless, many high proof whiskeys will still proudly state that they are non-chill filtered primarily because it is perceived as being more authentic.
Coloring
Though it may sound like the epitome of inauthenticity, the use of coloring is very common across all barrel-aged spirit categories, and not just lower quality ones. Many of the most highly respected Single Malt Scotches and Cognacs contain coloring, as do most dark rums.
Coloring is primarily done for two reasons: consistency, so each bottle within a brand looks the same, and to make a spirit appear older to consumers. The latter is not as nefarious as it may sound, some spirits don't acquire as much color as you'd think during aging, particularly when used barrels are used. So coloring is more to cater to consumer's expectations, not to deceive them outright.
The type of coloring that's used is called caramel coloring which, despite its name, doesn’t add any sweetness. The types of caramel used are E150a (typically used for Scotch) and E150b (typically used for Cognac). They actually taste bitter in their concentrated form and are not meant to affect the flavor of a spirit. Some argue it does affect flavor, actually, some say it has the positive effect of bringing blends together. But I think any impact it is minimal at best.
My general view of coloring is that while it seems a bit disingenuous, I don't think it degrades the product, so I don’t oppose it outright. But I do think there's something to be said for letting spirits exist as they are, and not worrying about appearances.
Sugar maple used for filtration of Jack Daniel's Tennessee Whiskey
Blending
Blending occurs across all spirit categories and can refer to two different things. One is mixing different batches of the same spirit to ensure each bottle is consistent from the next as is very common with all mass market spirits. The other type of blending is mixing spirits with different characteristics to create something new, such as blended scotch and many rums. In the case of the latter sometimes scores of different spirits will be used in a blend. It’s a bit like making a cocktail in a bottle.
Flavoring
Flavoring is a loaded word in the spirit-making world. It often brings to mind products like whipped cream vodka, salted caramel whiskey, and sour cherry rum. It probably goes without saying that I am not an avid fan of these types of spirits. Not that I'm above it, I just don't think they taste good. But a flavored spirit isn't an inherently bad thing. What generally sets them apart is whether the flavors come from natural or artificial sources.
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Natural - This can mean two things: infusing real whole ingredients - either by putting them in the still during distillation or steeping them afterward - or adding naturally derived essences. Many of these products are wonderful. Plantation’s Pineapple Rum, for example, is one of the tastiest beverages I’ve ever had. You could even make a case that the entire category of gin is a flavored spirit. It’s basically a vodka that is infused with botanicals during distillation.
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Artificial - These are the flavored vodkas and rums you see lining every backbar in America. Their flavors are usually provided by flavor compounds assembled in a lab meant to mimic a natural flavor. They are also usually heavily sweetened. To be fair, these products are not always bad tasting, though many flavors these days venture into the absurd. but they generally lack the nuances that make for a good cocktail ingredient. I like my rum to taste like rum. If I want some cherries along with it, I’ll add them myself. And of course,
That all being said, this is just my personal opinion. Drink whatever makes you happy.
Diluting, aka Proofing
Most spirits are diluted with water before they are bottled, this step is also called "proofing". After distillation spirits are typically between 60% and 95% ABV while anything you'll find on the shelf of a liquor store is generally taken between 40-50% (the minimum spirit strength in the United States is 40% ABV, in Europe it’s 37.5% ABV). This step is another key decision for the distiller. Alcohol intensifies flavor and even a degree of proof can make a big difference.
Some barrel-aged spirits are diluted before they go into a barrel, some after, some gradually over time, or a combination of all of the above.
Only a handful of spirits see no dilution. Some whiskeies are released at "cask strength" and some spirits are "distilled to proof", meaning the still is kept running until enough tails come through to bring the proof down to the desired level. Chilean pisco is one example of this.