There are many pieces of jargon in the world of whisky with each one making the entry to the category a little more opaque. Speaking of opaqueness in whisky, perhaps one of the least understood terms we use is chill filtration. In this guide we look at the different types of filtration used in the creation of your favourite whiskies and try to demystify the category for you. This is The Whisky Club's guide to whisky filtration.
If you're new to the world of whisky and want to knowledge up, have a look at the following guides:
The Whisky Club's guide to whisky for beginners
The Whisky Club's guide to making whisky
The Whisky Club's guide to reading a label
My whisky is cloudy. Is something wrong with it?
The likely answer is no. Single malt whisky naturally contains fatty acids which will come out of solution in cold conditions or in low alcohol (<46%ABV) environments. This will give the whisky a cloudy appearance as these compounds flocculate. If you've ever seen cloudy olive oil, it is the same reaction. Ugly, but ultimately harmless. If you want to see this in practice, take your favourite cask strength whisky and add a good splash of cold water to it. It will likely go milky. Or if you were lucky enough to score our 20 Year Old Blended whisky, it may have clouded slightly as we bottled it at 44.4% without chill filtration.
What is chill filtration?
Chill filtration is the practice of chilling a whisky down to between -2°C +4°C. This will cause any whisky under 46% ABV to go cloudy. It is then passed through a fine filter to remove the fatty acid compounds that cause the whisky to cloud up.
Is all whisky chill filtered?
No. Any whisky that is 46% ABV or above will likely be non-chill filtered. Similarly, grain whiskies do not need chill filtered. This is because they are distilled up to 94.5% ABV and don't contain the compounds that cause the whisky to go cloudy. So even at 40%, a single grain whisky will remain clear.
Why is whisky chill filtered?
The answer is simply aesthetics. A cloudy whisky on the shelf may appear unattractive to the consumer. Instead of raising the ABV to stop the cloudiness, companies decide to chill filter to keep the whisky looking crystal clear. This decision will have been taken for two reasons: paying less duty as higher ABV whisky attracts more alcohol duty; and giving the consumer a milder ABV to appeal to more palates globally. (Not everyone wants a cask strength monster of a dram.)
Does chill filtration remove flavour?
The biggest problem with this question, is we rarely get to try the same liquid before and after filtration outside of a blending lab. What I will say is that as a Master Blender, I did get to see these samples and one needed to be signed off vs the other. So, I can say to the majority of drinkers, there is no discernible difference. Occasionally, with fuller bodied spirits, the mouthfeel may have changed slightly, but never enough to mark the sample as out of spec. The reality is that chill filtration is removing natural compounds from a whisky, therefore at The Club, we strive for non-chill filtered releases just in case, but when we see amazing whisky that has been chill filtered, we will still procure it for our Members.
What other filters will a whisky go through?
Whisky is filtered at a few points in its life:
- When a cask is emptied, it will be over a coarse sieve-like filter. This removes detritus (like char) from the cask from clogging up the lines.
- Then the whisky will be chill filtered if appropriate.
- It will also go through a 10 micron filter before bottling to remove any small solids from the blend. These could be picked up from a tank or be small particles from the cask, especially if it is not chill filtered.
Can you use other filtration methods and bottle below 46% ABV?
Yes you can. If you let a whisky settle in vat or marry in cask, it will flocculate. This brings these fatty acids and oily notes out of solution. They are colloids (not liquid or solid) and sink in a vat as the spirit horizons out. The clear liquid on top can then be siphoned off leaving the flocs behind. This is a natural process, and mimics what happens when a whisky is chilled. The natural flocculation over a few weeks is a less-intense process, and likely leaves more of the fatty acids behind in solution. In Scotland, this process can happen in a marrying cask over 4-8 weeks. This allows a distillery to chill filter at a higher temperature, again leaving more compounds in solution.
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