The complete guide to non chill-filtered whisky

Non chill-filtered whisky (also styled non-chillfiltered and even un-chillfiltered whisky) is one of those terms in the whisky industry that is widely seen, read, and heard…and yet few drinkers truly understand what it means or signifies.  In that respect, it’s a bit like sour mash in the bourbon industry – a term you see printed on the label; a statement that supposedly has a positive connotation, and yet the majority of consumers view it as mumbo-jumbo…not really appreciating what it means, but just happy to enjoy what’s in the bottle.  So what is non chill-filtered whisky?  What is chill filtration?  And how do you un-chillfilter something?  Is a non chill-filtered whisky better than a whisky that has been chill-filtered?  Let’s dive in…

Whisky is a distilled spirit.  The distillate is produced by boiling a beer, which was fermented from a mash made from cereal grain(s).  The vapour (i.e. steam) captured from that boiling process condenses back into liquid form, and then spends a few years aging in an oak cask.  We’ll bypass the minutiae of the chemistry involved, but the executive summary is that the final outcome of all those combined processes is a delicious drink that contains – amongst other things – alcohol, water, congeners, protein chains, oils, and fats.  These oils and fats are triglycerides which are made up of compounds that have more technical-sounding names like fatty acids and esters, which we further identify as ethyl esters and alkyl esters.  It’s chiefly the family of ethyl esters that form the backbone of what’s being discussed in this article, but – in order to avoid going into the chemistry and behaviour of lipids, lactones, ethyl-dodecanoate, ethyl-hexadecanoate, and ethyl-palmitate – we’ll keep the terminology simple:  Oils and fats will do.

It’s those oils and fats in the whisky that form the story here.  Some consumers like to take their whisky with a splash of water, or to have it with ice.  The addition of either to the whisky can create a haze effect that causes the whisky to turn slightly cloudy – a visual phenomenon that, in itself, has no impact on the quality or flavour, but came to be considered an aesthetically undesirable outcome.

What’s physically occurring is that those oils and fats in the whisky are reacting to the water/ice and they’re changing in their composition and behaviour.  At a molecular level, the change in temperature or dilution (or a combination of both as the ice melts) causes the esters within the oils and fats to bind or clump together, forming micelles.  This, in turn, creates a cloudiness or haze in the whisky.  The scientific term for what’s happening is flocculation, aka floc, which can be described as “interparticle collisions promoting the formation of larger particles, which come out of suspension in the liquid to sediment”.  The process is also sometimes referred to as louching.

When it comes to your whisky, haze/cloud/floc is entirely a cosmetic issue.  But beauty is in the eye of the beholder, and it seems the general public expects a crystal-clear whisky in their glass.  Enter chill-filtration…

There’s an origin story to this that is probably more a well-spun tale, rather than an actual occurrence that took place.  You may even have heard a whisky brand ambassador tell the story at a tasting event.  It goes something like this:  In the mid-1950’s, in the wake of World War II, a large consignment of Scotch whisky was shipped from Scotland to America.  The ship berthed in the USA in the middle of a freezing winter, and the cases were unloaded on to the docks.  The local importer came to collect the whisky, but noticed that the liquid in all the bottles was cloudy.  Believing the whisky was of dubious quality or had somehow “gone off”, the consignment was promptly rejected, re-loaded back on to the ship, and sent back to Scotland.  Of course, the whisky was perfectly fine…it’s just that all the oils and fats had flocculated due to the freezing temperature.  But the damage was done:  Determined to ensure such a debacle would never be repeated, the Scots subsequently began to chill-filter their whisky, so as to keep the liquid visually pristine in all conditions.  Like so many other things in life, emphasis was put on outward appearances.

 

What is chill-filltration  or chill-filtering?

Chill-filtration is the act of chilling the whisky down to a low temperature (typically anywhere between -4^o and 4^o degrees Celsius), and then passing the liquid under pressure through some form of barrier filter.  (Remember, the freezing point of alcohol is significantly lower than that of water.  Whilst water freezes at 0^o C, pure alcohol’s freezing point is -115^o C.  The freezing point of whisky at around 60% ABV is approximately -37^o C).  At the chill-filtering temperature of around 0^o or so, the oils and fats in the whisky clump together and floc, and they can be picked up by the filter.  Or, more crudely, they are stripped out of the liquid.  The whisky that passes through to the other side of the filter is now minus the offending oils and fats, and will now remain crystal clear if the end consumer chooses to add water or ice to their dram.  Whisky distillers, producers, and bottlers thus choose to chill-filter their spirit so as to provide an aesthetically-pleasing product that meets the visual expectations of their customers.

 

What is non chill-filtered whisky or un-chillfiltered whisky?

As the term implies, non chill-filtered whisky is simply whisky that has not been chill-filtered.  In other words, it’s the natural product that hasn’t been further treated or adjusted, at least for the purposes of aesthetics.  Of course, producers do adjust their spirit further in selecting its bottling strength or proof:  They elect whether to dilute the spirit with water and thus whether to bottle the whisky at 40% ABV, 43%, 46% or higher, or to simply leave it at “cask strength”, just as it was when it came out of the cask.  The choice of bottling strength plays an important part in the chill-filtering narrative, as we’ll explore right now…

 

What about the alcohol strength and what’s so special about 46%?

As a general rule, those pesky oils and fats are more prone to cause haze or cloudiness when the whisky is at a strength below 46% ABV.  The vast majority of Scotch whisky – both single malts and blends – is bottled at 40%, or occasionally 43%, and these whiskies will almost universally be chill-filtered to combat the risk of haze.   

Generally speaking, whisky that is left un-chillfiltered is typically bottled at 46% ABV or higher.  The accepted wisdom is that, at 46% or higher, the oils and fats are less likely to floc and haze up at room temperature – and hence chill-filtering is considered unnecessary.  The reason for this 46% threshold is because oils and fats behave in a different manner when suspended in alcohol than they do when suspended in water.  They essentially remain soluble in alcohol at room temperature, but (effectively) become insoluble or flocculate in water.  46% is typically the balance point between the two forms of behaviour, although the variable here is room temperature, which can vary between 18^o and 24^o C, depending on where you are in the world.  And that’s before you take your drink outside!

 

Will non chill-filtered whisky at 46% ABV still floc and haze up?

In short, yes.  If you add water to the whisky, you are instantly diluting it below 46%, and the conditions that promote floc will apply.  Even more so if the water you add is particularly cold, and especially so if you also add ice.

For this reason, many whiskies that proudly state “Non chill-filtered” on the label will usually also have something on the packaging to advise the consumer that a haze may develop.  Two typical examples are shown below…

It’s been observed and commented on that some whiskies at 46% can still floc in the bottle at colder room temperatures, without any addition of water.   This is usually on a brand-by-brand basis, and is a function of the specific chemistry of the whisky – which is ultimately a function of far too many variable parameters (yeast, fermentation, still shape, the condensers, cask type, oak contribution/extraction, etc).  For some whiskies and other spirits, some industry people assert that 50% ABV is the more appropriate threshold to prevent the esters from floccing. 

However, what we see as floc in the bottle can also be a function of the quality and nature of the dilution water used at bottling stage.  If the dilution water – that is, the water used to bring the spirit down from cask-strength to 46% – has not been sufficiently de-mineralised, there can be calcium or magnesium compounds in the whisky that will also promote floc.  These minerals behave independently of temperature, and their appearance is referred to as being “irreversible floc“.  (There has been some commentary that Ardnamurchan’s bottled whisky falls into this camp, as their diluting water is sanitised chiefly with UV technology and with minimal filtration, thus leaving some mineral content).

The inference is that the floc from oils and fats is reversible…achieved by simply warming the liquid back up again.  But we need to appreciate that there are other compounds in the whisky that can promote floc or haze, and these other compounds won’t necessarily be removed by chill-filtration.      

 

Is non chill-filtered whisky good or bad?

In truth, that’s not the right question to be asking and, in any event, the answer is subjective – different people will have different views on the matter, subject to personal taste and preference.  Or, more accurately, their opinion will be informed by how good their palate is, and their actual capacity to detect the difference!  The more interesting question to ask is this: “What difference does it make to the flavour or quality of the whisky?”   So let’s answer that question now…

 

What difference does chill-filtering make to the flavour or quality of the whisky?   

As anyone who appreciates food or cooks will tell you, fat = flavour.  The oils/fats in the whisky carry the flavour-giving esters.  It stands to reason that if you remove some of these esters by chill-filtering, you are – by definition – removing some flavour.  Just how much flavour is being removed depends on the properties of the whisky and how aggressive the chill-filtering is.

Another feature of fat/oil is its texture.  Fats and oils can be viscous, syrupy and…well…oily in nature.  It is a physical property we perceive via our sense of touch, and in the world of whisky, this is described as the mouthfeel.  Again, by definition, if you remove some of these esters, you are removing compounds that contribute to the whisky’s overall mouthfeel.  Chill-filtering can thus impact a whisky’s tactile properties.

The position thus held by many whisky enthusiasts and purists (and more than a few brands/producers, particularly Burn Stewart) is that chill-filtering is thus an undesirable practice:  It robs the whisky of some of the flavour and texture that was originally in the spirit.

Note that this position or mindset is not a new or recent development.  Whisky writer, Jim Murray, in his 1997 book “The complete guide to whisky”, made the point that Laphroaig, in particular, was a whisky whose character suffered significantly from chill-filtration, and that chill-filtered Laphroaig expressions bottled at 40% were noticeably different in flavour and texture from the non-chillfiltered cask-strength 10yo bottling released in 1995. 

 

How can I test this or check it out for myself?

If the situation is as black-and-white as the purists insist, it would be great to prove it by comparing the chillfiltered and unchillfiltered versions of the same spirit.  Unfortunately, there are virtually zero commercial brands that offer the exact same expression in both forms.  However, you can actually check this out for yourself at home.  You simply need three things:  (1) A non chill-filtered whisky, preferably one that’s cask-strength at around 55-60% ABV or so.  (2) The freezer in your kitchen.  (3) Good quality, non-bleached, conical coffee filter papers.

First, pour out some of the cask-strength whisky into a smaller sample bottle (say 50ml), and seal it to keep it fresh.  This will be your reference dram.  Then put the bottle of whisky in the freezer for at least four to six hours.  Domestic freezers typically operate at around -18^o C, so the whisky should remain entirely liquid.   Then take two coffee filter papers, (place one inside the other to create a “double” filter), and place the cones over a glass.  Once the whisky has spent enough time in the freezer, take it out and immediately pour, say, 50ml into the coffee filters.  The liquid will slowly drip through the filter paper and what you have in the glass underneath is, officially, chill-filtered whisky.  Providing the coffee filters are good quality and sufficiently dense, they’ll have stripped out some of the ester compounds.  (Yes, those oils and fats).   You then need to wait for this glass to come back to room temperature, so perhaps put some cling wrap or a lid on the glass to prevent it from oxidising too much whilst it heats back up.  Once it’s there, you can pour a glass of the reference dram that you siphoned off earlier and directly compare the two, like for like.  Decide for yourself if the chill-filtered version is perceptively different in flavour and/or mouthfeel.

 

Which whiskies or brands leave their whisky un-chillfiltered?

In a trend that’s steadily growing, a number of Scottish single malts opt to bottle their standard, flagship expression at 46% or higher and leave the whisky non chill-filtered.  Well known examples are Ardbeg, Bunnahabhain, Tobermory, Deanston, Bruichladdich, Craigellachie, and Glendronach.  (And, yes, plenty of others).

 

Is there a difference between blends and single malts when it comes to chill-filtering? 

In one sense, yes.  Generally speaking, single malts are chill-filtered at temperatures around 0^o to +4^o C.  However, blends need to be treated a little differently.  Blends are a combination of (1) malt whiskies (barley) that are pot-distilled, and (2) grain whiskies (corn or wheat) that are continuously distilled in columns to a much higher strength and level of refinement.  Owing to the processes involved and the nature of grain whisky, the distilled grain spirit has a lower concentration of fatty acids and esters.  As such, so does the resulting blend (i.e. the malt + grain), and so blends need to be chill-filtered more aggressively at lower temperatures (i.e. -4^o C) for the lower concentration of oils and fats to adequately floc and be captured.   Accordingly, a greater quantity of the oils and fats are removed from the malt component of the blend than might otherwise apply! This is, arguably, one reason why cask-strength enthusiasts accustomed to the mouthfeel of single malts can find blends “thin”.  Whisky & Wisdom coined this experience as “having the cask-strength blues“, and you can read our feature article on that topic here.

There are a small handful of non chill-filtered blends on the market, bottled at 40-43% ABV, typically from the likes of Compass Box and Pràban na Linne.

 

Do other drinks employ chill-filtration before bottling?

Yes, many other commercial spirits brands chill-filter their product for the same reasons discussed above, e.g. vodka, gin, and rum.  Some gins can be chill-filtered quite aggressively, with the temperature taken as low as -10^o.

Chill-filtration also plays a major part in beer production.  In addition to seeking a clear liquid with no haze (craft beer and hazy IPA’s aside), beer has the added complexity of needing to kill off any live yeast and bacteria left between fermentation and bottling.  This can be done either with heat pasteurisation or, more commonly these days, by chill-filtering.  The beer industry typically refers to the process as cold-filtering.  Australian readers may recall the beer wars of the mid-1990’s when two large beer brands tried to expand their consumer base and entice non-beer drinkers into the category with a product that was less challenging.  Carlton Cold and Hahn Ice were heavily marketed as cold-filtered beers, with both marketing campaigns espousing the “clean, crisp taste”.  Yes, they were indeed clean, but most regular beer drinkers found them too clean, dismissing them as tasteless and bland.

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So there you have it – we trust you found this deep dive into chill-filtering helpful and informative.  If you subsequently try the “chill-filtering at home” exercise outlined above, be sure to come back and share your experience and conclusions in the Comments section below – doubtless other readers will be keen to hear your thoughts.

Cheers,
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PS…if you enjoyed this article, you might also like our other “explainer” articles:

The complete guide to peat and peated whisky

The whisky lover’s complete guide to sherry

The complete guide to oak, casks, & whisky maturation

The 1980’s heavy metal guide to whisky

Oxidation – does whisky go off in the bottle?

Corked whisky – fact or myth?

The stink about sulphur