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Chill Out: What You Need to Know about Bourbon Filtration

When Jim Beam Repeal Batch was released a few years back to commemorate Prohibition’s repeal, a phrase on the label in bold letters caught my eye: Non-Chill Filtered. What did that mean, exactly? Was this unique? Is all bourbon filtered? My curiosity was piqued.   



Bourbon Filtration 101


Yes, all bourbon is filtered … unless you’re thieving directly from the barrel (which I have to say is quite an experience!). Most bourbon, when dumped from the barrel, passes through a bed of charcoal and mesh to remove bits of char and any solids from the finished spirit.


Isn’t that what Tennessee Whiskey is? Not exactly. These spirits, like Jack Daniels and Dickel, use what is called the “Lincoln County Process'', where the fresh distillate passes through charcoal (typically made from maple trees), before the distillate is placed in the barrel for aging. At Jack Daniels, this pre-aging filtration can last for several days, and by bourbon’s definition, voids the spirit from being bourbon (as bourbon can only be filtered after it has aged).


Most distillers utilize a chill filtration, whereby the charcoal-filtered bourbon is then chilled in large tanks down to 28 degrees. Why? To make the finished product look good. What’s that you say? 


Have you ever chilled your bourbon on ice, only to see it cloudy, with strange, opaque bits floating in your glass. That, my friends, is “whiskey flocking”.  It’s really evident if you place a bottle in the freezer for several hours and then pour yourself a glass (Be sure to tell your spouse you’re conducting a science experiment!).


Those bits often clump together in the bottle or glass, and for many, may be unattractive. Though, they aren’t harmful. Rather, it’s some of the fatty acids, protein, and esters that, when chilled sufficiently, fall out of the whiskey, clump together, and are then visible to the naked eye. When the whiskey warms up a tad, the flock will return to the solution and disappear once again.


Non-Chill Filtration   


The issue of flocking tends to appear in lower-proof bourbons - typically those under 95 proof. That’s why you generally won’t see flocking in non-chill filtered products that are bottled at a higher proof, such as barrel-strength products.


Do you want those proteins, oils, and esters in your glass? That depends. For decades, nearly all products were chill-filtered. In fact, it was Russian distillers in the 15th century that discovered these oils could be filtered off of vodka when ice was used to chill the alcohol.


As bourbon’s popularity began to rise in the 1990s and early 2000s, many visitors enjoyed sampling bourbon straight from the barrel in its “natural state”. What they discovered was that by leaving the fats and oils in the product, the product was often more flavorful and led to a thicker mouthfeel as the bourbon struck the palate. 


Whether that’s imagined or not, I’ll leave to your personal preference. Truth be told, I’m not sure I could tell the difference between a blind tasting of the same spirit - one that was chill-filtered and one that was not. I do know, though, that when I see that phrase - non-chill filtered - on a bottle, it tends to find its way into my basket.


Shopping Tips  


If you’re looking to specifically try a bourbon that isn’t chill-filtered, be sure to view the label carefully. Many of your mainline products from Beam, Heaven Hill, Buffalo Trace, and so on tend towards the chill-filtration to deliver a more consistent finished product. However, certain releases, such an Elijah Craig Barrel Proof may be non-chill filtered if the distiller feels it enhances the flavors.  Wilderness Trail and Green River are some of the few distillers that almost exclusively release non-chill filtration products.



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