Turn over a bottle from an enthusiast-focused distillery and you will often find two phrases in small type: “non-chill filtered” and “natural colour”. They are offered as guarantees of integrity, and their absence from a mainstream label is read, by some, as a confession. The reality is more interesting than either camp admits. Both processes are real, both are widespread, and both change the whisky — though by less, in most cases, than the argument around them suggests. This guide explains what each does, why distilleries use them, and what the label phrases actually promise.
Our label guide covers where these phrases sit among the others; this is the detail.
Why whisky goes cloudy
Whisky contains compounds that are soluble in alcohol but less so in water: long-chain fatty acid esters, proteins and some of the oils extracted from the cask. At bottling strength above about 46 per cent they stay dissolved. Below that — and particularly when the whisky is chilled, or when water or ice is added — they come out of solution and form a haze. The whisky turns slightly cloudy, and in a cold glass it can look like dishwater.
This is harmless. The haze is flavour compounds, not contamination. But a customer who buys a 40 per cent whisky, adds ice and watches it go murky does not know that, and for most of the twentieth century distillers judged that cloudy whisky was returned and clear whisky was not.
What chill filtration is
The solution is to make the haze form before bottling and remove it. The whisky is chilled to somewhere between about minus ten and plus four degrees, which causes the compounds to precipitate, then passed through fine cellulose or paper filters that catch them. What comes out is a whisky that will stay bright and clear at any temperature and any dilution.
It is quick, cheap and almost universal for whisky bottled at 40 or 43 per cent. Most mainstream Scotch, Irish and Japanese whisky is chill filtered. Most bourbon is too, though the term is used less.
What it removes, and whether you can taste it
The filtered compounds contribute to mouthfeel — the oily, coating texture of a heavier whisky — and, to a lesser degree, to aroma and flavour. Remove them and the whisky is marginally thinner and cleaner. How marginal depends on the whisky: a heavy, oily, waxy spirit loses more than a light, delicate one, and whisky at 40 per cent loses more than whisky at 46 because more is precipitated.
Whether a drinker can tell is the contested part. Blind tests have produced mixed results, with experienced tasters sometimes able to distinguish filtered from unfiltered versions of the same whisky and sometimes not, and preferring the filtered version as often as not when they can. The honest summary is that chill filtration takes something away, that the something is small, that it matters more in some whiskies than others, and that the difference is rarely the biggest thing separating two bottles.
The 46 per cent convention
Because haze forms below about 46 per cent, that figure has become the standard bottling strength for whisky that is not chill filtered: it is the lowest strength at which the whisky stays clear without filtering. A bottle at 46 per cent is very likely non-chill filtered whether or not it says so; a bottle at 40 per cent almost certainly is filtered. Our understanding ABV guide covers what the extra strength does beyond preventing haze, and the bottling terms guide covers how it fits with cask strength and single cask bottlings.
What colouring is
Whisky’s colour comes from the cask — our maturation guide and wood and flavour guide explain how — and it varies enormously from cask to cask. Two casks of the same whisky filled on the same day can emerge a decade later as pale straw and deep amber. For a brand that wants every bottle of its 12 Year Old to look the same, that is a problem.
The solution is spirit caramel, E150a: a flavourless, dark-brown colouring made by heating sugar, added in tiny quantities to standardise colour from batch to batch. It is permitted in Scotch, Irish, Canadian and Japanese whisky, and prohibited in straight American whiskey, which is why bourbon colour varies and Scotch colour does not. The quantity is small — a few drops per litre — and the regulations require that it be used only for colour and not for flavour.
Whether you can taste it
At the quantities used, E150a is widely held to be undetectable by taste. Some drinkers insist they find a faint bitterness or a slight flattening; most blind tests have found nothing. What colouring certainly does is remove information. A deep amber whisky might be deeply sherried, or old, or coloured; without the “natural colour” statement there is no way to know from looking. Enthusiasts object to it less for what it does to the flavour than for what it hides about the cask.
Why distilleries do both
Consistency. A brand sold in dozens of countries, in a market where the customer buys the same bottle every month, needs each bottle to look and behave like the last. Chill filtration guarantees clarity; caramel guarantees colour. Both are cheap, long-established and, for the overwhelming majority of customers, invisible. A distillery that skips them is making a choice to accept variation — pale batches, cloudy glasses — in exchange for a small gain in character and a large gain in credibility with the minority who care.
What the label phrases guarantee
“Non-chill filtered” means exactly that: the whisky has not been chilled and filtered. It will almost always be bottled at 46 per cent or above, and it may go hazy with ice. It does not guarantee the whisky is unfiltered altogether; most is passed through a coarse filter at room temperature to remove cask fragments.
“Natural colour” or “no added colouring” means no E150a. The colour you see is the cask’s. Some markets — Germany is the best known — require the opposite declaration: whisky with caramel must say so, usually as mit Farbstoff, which makes a German-market bottle a useful check.
The absence of either phrase means nothing definite but usually means the process was used. Few distilleries skip chill filtration or colouring without saying so, because the statement is the point.
A test you can run at home
If you want to see chill filtration for yourself, take a non-chill filtered whisky at 46 per cent, pour a measure, and add an equal volume of cold water. Within a minute it will turn faintly cloudy, sometimes dramatically so; that haze is what filtration removes. Do the same with a 40 per cent mainstream whisky and it will stay clear. Then taste the two diluted glasses for texture rather than flavour: the unfiltered one will usually coat the mouth more. It is a small difference, and it is the whole of the difference, which is a useful thing to have experienced before taking a side in the argument.
For colouring, the test is harder because the colour is the only evidence. The nearest thing is to compare a “natural colour” bottling from a bourbon-cask whisky — typically pale gold — with a mainstream bottling of similar age and cask that is noticeably darker. The darker one has either had more active wood or a few drops of caramel, and without the label you cannot know which.
How much it matters
Less than the argument suggests, and more than the mainstream admits. If you are choosing between two whiskies and one is non-chill filtered at 46 per cent and the other is filtered at 40, the first will usually have more texture and will certainly have more alcohol, and both differences are worth having. But the cask, the age, the spirit and the distillery matter far more, and a filtered, coloured whisky from a great cask will beat an unfiltered, natural one from a poor cask every time. Treat the phrases as useful information about the producer’s priorities, not as a measure of the whisky.
