Non–Chill Filtration versus Chill Filtration

Today, I have something a little bit different from my usual ramblings: a genuine whisky experiment. So-called whisky experiments are nothing new; we hear about them from time to time. Often, however, they are basically just an unusual cask selection, either for full maturation or as a finish. I’ve heard that Glenfiddich are big fans of this, and we’ve seen others have a go too, such as Glen Moray’s cider cask project, or Bushmill’s acacia-finished distillery exclusive. Regardless of what you may think of these types of releases, none of them are much of an experiment in the true sense. For that, you should control all the variables except the one you want to investigate. Although I’ve yet to see for myself, it sounds like Waterford are the kings of this approach. (Mark would be the guy to ask.)

I was recently given the opportunity to do a proper experiment with whiskies bottled with and without chill filtration. A company (who prefer to remain nameless) had conducted their own analysis at the request of some visiting guests, and I was sent the same samples to see what I made of them. Unlike the original recipients, I had the luxury of more time to play around with the different versions of this malt. I first tasted them knowing which was which, then did a blind tasting and finally a repeat of the former. I even had enough left over to try some other things like refrigerating to compare the cloudiness. It was really fun, and I have some results that may or may not align with the expectations of whisky drinkers/producers!

The tasting notes I experienced were pretty consistent, apart from one which caused me a little confusion. On the first test, I encountered some earthy mushroom notes, but they seemed to disappear in the second (blind) experiment. I was hellbent on trying to figure out which sample had it originally, thereby skewing my judgment, while simultaneously annoying me! This was another good reminder to myself to practice what I preach, to try whiskies more than once to make sure I get to know them properly!

They were all coppery gold in colour, and so impossible to differentiate, but a quick swirl test could show you the noticeable differences in viscosity. I tried hard not to pay any attention to that until the last test, in an effort to properly ‘blind’ myself. Below are my (kind of repetitive!) notes for the three subtly different versions of this non-age stated sherried malt.

Sherried Malt Non-Chill Filtered (Natural Colour), 43%

On the nose: it is sweet with watered-down golden syrup and honey, or a weak caramel. With sherried whiskies, I usually get red dates and goji berries; they are present here, but more like the water they’ve been soaked in, rather than the pungent fruits themselves. Quite aggressive on the nose, almost like inhaling the fumes from the washback, both sour and solvent notes. Rubber comes through with a chalky dryness to the nose. Bitter with citrus rinds and ground cloves. There is wet wood and damp soil and a weak scent of strawberries. It is very malty, with lots of cereals coming through; vanilla toasted oats dusted with icing sugar and fresh pine furniture polish.

In the mouth: sweet like a thin sugar syrup. It is very bitter; the zest and rind of grapefruit mingle. A tickle of white pepper is slightly tannic and drying; however, the liquid was slightly oily to begin with. The mouthfeel is pretty thin and watery. There are a lot of porridge-y notes with something similar to ground nutmeg or cloves. Quite astringent, with a rubbery aroma.

The finish is very short; the flavours fade quickly and leave behind a very bitter dry mouth; however, the sides of my tongue were slightly oily. There is an aftertaste of black grapes and a feeling of furry fruit skins.

Sherried Malt Chill Filtered (Natural Colour), 43%

On the nose: sweet with honey and golden syrup. There is also an artificial orange sweetie flavour. Again quite aggressive on the nose, with washback maltiness giving a sour and solvent tang mixed with porridge oats. Chalky tartness with sweet powdery red apples and red berries mixed in lemon juice. There is a woodiness to it and presence of citrus rinds that makes it seem bitter. Tannic cloves and dense rubber override the scent of ripe red berries.

In the mouth: sweet with an icing sugar sensation that begins to dry. On the top and sides of the tongue there was the thinnest film of oil. Bitter and acrid with a stronger presence of white pepper. When the oil dries out it feels strangely like you have just finished smoking; no smoke, per se, but an astringent tannic linger. Strawberries and marmalade are present also.

The finish is short with an aftertaste and sensation of drinking a dry white wine. There is a fermenting fruit feeling on the back of the mouth and throat that is both burny and bitter. The sides of the tongue remain slightly oily, but the rest of the mouth dries out.

Sherried Malt Non-Chill Filtered (Natural Colour), 47.5%

On the nose: golden syrup and honey notes are richer in this whisky, whilst the fruity notes, like ripe strawberries and other berries, give a sense of thick fruit jam. Again quite aggressive with that washback solvent sourness; the malted oats and gojis combine for a nice berried porridge aroma. There is a hint of rubber with chalky powdery icing sugar. Orange with a hint of cloves, sweetened with toffee, comes through strongly.

In the mouth: very sweet and honeyed, with a sensation of drinking fruit juice. Again, there is the feeling of powdered sugar on your teeth and a bitter, astringent, dryness. However, the sides of the tongue remain oily with a white pepper burn. The mouthfeel is a lot more oily and viscous with the sensation of eating a very lightly salted pineapple. The notes of marmalade and jam are present, along with a more thick, jammy mouthfeel. There is also a small hint of rubber on the back of the tongue.

The finish delivers sweetness and a chilli heat. The tannins remove these flavours from the mouth, but they continue to linger on the throat, with the slightest of tickles on the sides of the tongue. The oily fats make the finish short to medium with a bitter and rubbery end.


In order of preference, I enjoyed the NCF 47.5% the most, followed by the CF 43% and finally the NCF 43%. This may be a little surprising if you subscribe to the convention that chill filtering has a negative effect on whiskies. Honestly, the nose and mouth of the lower ABV whiskies were very similar, but on balance, I preferred the chill filtered version. Both felt pretty thin, to the point where I questioned whether I had mixed up my glasses a couple of times! However, after testing them in my three experiments, I came to the same conclusion. In this case, the chill filtering process slightly reduced the largely unpleasant bitter, tannic nature of the whisky that was prominent at the lower ABV. Its effect on the mouthfeel or texture of the spirit was minor, in my opinion.

My clear favourite was the 47.5% non-chill filtered version. It was tastier and more satisfyingly viscous, obviously so when sampled alongside its weaker siblings! To me, it really brought home how much the experience of a whisky can suffer when it is diluted down close to the legal minimum. It may be necessary for mass market products to lower prices, but it is a big compromise. Aesthetically, even simply swirling the liquid in a glass, it is more appealing than the other two more watery spirits.

What I learned from this experiment is that even a relatively small boost in bottling strength greatly improves the whisky, to my taste anyway. However, I do generally prefer cask strength whiskies and I tend not to water them down, so it’s not a surprising conclusion for me. Your mileage may vary. This reminds me of a tasting I attended where I watched aghast as two older gentlemen poured as much water as there was whisky into their glass before even trying it. I always say that people should enjoy whiskies however they want to, add a splash of Irn Bru if you want, whatever, but… at least try it first, right? In catering, it’s rude to salt and pepper your food if you haven’t tasted it first. Perhaps a similar rule should apply to whisky drinkers. As for the chill filtration process, in this case, I feel that it actually made this whisky taste nicer at the lower ABV. I guess this is not the case for all whiskies, but chill filtering could possibly take away flavours that people find unappealing. It is a good experiment and, as taste is subjective, chill filtering might not be a thing you should turn your nose up at. If it is possible, I encourage you to take part in a similar experiment and the results it yields may surprise you.

    1. Dora says:

      Thanks for the comment PB! In this case definitely so, the higher strength made the clearest difference. For me it shows that the choice of so many whisky makers to bottle at 46% and above is justified. I’m sure in some cases chill filtration could have a more negative effect, and as always it comes down to personal preference.

  1. Dan w says:

    Interesting article Dora. I’ve heard it said before that the effect of CF on whisky is over-emphasised.

    What I think is the case (and you touched on this in your piece) is that chill-filteration often goes hand in hand with other factors that negatively effect the whisky. Lower bottling strength, artificial colour. And if the manufacturer is willing to increase profit margins by bottling at a lower strength to get more bottles out of the cask. Maybe they’re willing to cut corners in production to get a higher yield or more runs in a day. Maybe they’re prepared to spend a bit less on casks.

    Whereas your distillery which is trying to catch the attention of the discerning customer and so proudly displays ‘no chill filtration’ on the label they also bottle at 46% or above, natural colour. Maybe they spend a bit more on casks because they know their customers will work it out of they don’t and go elsewhere.

    Just a thought.

    1. Dora says:

      Hi Dan, thanks for the comment! You have made some very good points and it does make one wonder what other “cuts” some distilleries are making. For me, in this instance, I felt that the CF had a positive effect on the whisky I sampled by taking away the bitterness. However, exactly why that was I can’t say. I will leave that to the true scientists 😀

  2. Rolf Isaksen says:

    Very interesting result, Dora. I always hope that the un-chillfiltered will «win» in head to head comparisons like this. Same if it is about natural colour vs E150a. I guess it is a good thing that it doesn’t affect the whisky that much, but I’ll continue to favour naturally presented whiskies because it just feels better psychologically 🙂

    1. Dora says:

      Hi Rolf, thanks for the comment! As this is the only time I have tried an experiment like this, CF won in the head to head for me at the same ABV but I think with other whiskies there will be a different result. With the caramel colouring, I reckon there would be a sweeter liquid for a start but that could mean a good thing for some people who prefer a sugary dram. I’d be interested to see the results of an experiment like that… maybe in the future! Watch this space!

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