More and more often now we are seeing whisky manufacturers take a more purist approach by avoiding chill filtering and colouring of their products. But what exactly are these processes, what is the reason for them and how does it affect the end product?

Firstly, lets talk about colouring. As the single malt whisky industry grew, its clientele began to expect a level of consistency between any two bottles of the same labeled product. One large area of inconsistency comes from the flavourings and colourings imparted by the cask used to mature the distilled malt whisky.

As I have mentioned in another post, the flavour aspect is controlled by the skillful blending of whiskys across casks and even ages from within the distillery. The colour tone can also be normalized in this manner, but more typically a standardized rich golden tone is provided with the addition of caramel for colouring.

Chill-filtering has an entirely different purpose. Say for example, you poured directly from a cask into a bottle. How would that be any different from a carefully blended and filtered single malt? First the whisky will contain small ‘chips’ and impurities from the inside of the cask (I’ve heard these referred to as coals). These are entirely harmless, but offputting to most consumers. These can be mostly removed using regular filtering (through a metallic filter mesh). The second difference is that the malt that is not chill-filtered will contain natural oils and proteins present from the distillation and also extracted from the cask. These oils can cause the whisky to become cloudy when chilled or mixed with water which is again offputting for the average consumer.

Chill-filtering is a process (created I think sometime in the early 20th century) whereby the liquid is chilled to around freezing point (0°C) . This causes the natural oils and proteins to clump, and once passed through a filter these elements can be more effectively removed. This process also removes the sediment and coals.

A purist typically does not care for unnatural additions to his single malt, and in fact would celebrate differences from one cask to the next. In fact, becoming familiar with how different a whisky can be between casks really does lend some knowledge to what factors do affect the final product in terms of flavour, colour, aroma and finish and to how important the cask maturation is.

The same purist would typically also not care for any extractions from the product, and the chill-filtering process does just that. Personally, I have no problem with a single malt clouding up with the addition of water, and instead celebrate the fact that the whisky almost certainly has flavour aspects and a texture that would have been very different had it been chill-filtered.

As I mentioned, more and more single malts now label the fact that they are unchill-filtered or colour free. Custom bottlings are rarely touched in this manner, and the Blackadder bottles I own contain a fair amount of the sediment talked about earlier. The Signatory collection have some great cask strength and virtually untouched malts. Most cask strength whiskys are probably non-chill filtered as well, for example the Aberlour A’bunadh.

Please feel free to post your feedback in the comments. I’d love to know if this helped anyone clear up some of the meaning behind the terms.