I've heard of it but I'm too Afraid to ask. What actually is chill filtration?

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I’ll start from the beginning.

Now all whisky will undergo some kind of filtration. Through some sort of mechanical filter like steel, cellulose or a nylon mesh. To remove small pieces of wood particles that may detach from the barrel or any minor sediment that got through the distillation process.

In some alcohol distillation activated carbon (charcoal treated with oxygen) is used to filter the spirit. The surface area of 1 g of activated of the charcoal is larger than a football field. The molecules adsorb onto the surface filtering the solution.

Imagine the surface like a large car park with each molecule fitting in and finding a space. The larger the car park (surface area) the more cars can be parked (molecules adsorbed). Incidentally, this also the reason activated charcoal is one of the treatments for alcohol poisoning. They give you a black gloopy solution and you drink it. Adsorbs all the alcohol.

The problem is, it doesn’t discriminate between the good stuff you want, and the bad molecules you don’t. This takes away a lot of the flavour. And you know that’s good for say vodka. Where a lack of flavour is sought after, but in whisky. Not so much.

Then there’s Tennessee whisky. It often goes through Lincoln County Press. A process invented by the man who taught Jack Daniels how to distil Nearest Green. Whereby the whisky is filtered through a sugar maple bark before its put in the barrel.

The whisky is only filtered before it enters the barrel with no aggressive filtering takes place after aging. The exception to this is Jack Daniels Gentleman Jack which undergoes filtering before and after.

Sorry I got a little side tract there but I’ve got what you came for.

When whisky gets cold a haze can form. The haze is sometimes referred to as Scotch mist. The dissolved aldehydes and esters (flavoury oils) precipitate if its too cold. Incidentally because of how well alcohol dissolves oils, this doesn’t happen in whiskies above 46% ABV. However, someone (probably at Diageo but unconfirmed) decided the mist is deemed to be off putting to the consumer. So they began chill filtering to remove it.

The whisky is chilled below 0 ^o C, or sometimes as low as -12 ^o C. This precipitates out the thicker oils as a sludge. The mixture is then passed through a series of mechanical filters which remove the sludge. The filters are usually made of a compressed wood pulp to minimise the impact on flavour. Leaving the whisky bright and clear. Crystal clear spirit looking like a highland spring.

Not everyone agrees it has a positive impact. Chill filtering can remove mouthfeel as well as flavour components.

I spoke with a member of staff at Dalwhinnie and he told me he sees it as taking something out, taking something away. That’s always going to impact the final product. 

So in your finer single malts you’ll proudly see displayed non-chill filtered, as a badge of honour and a point of pride.