Anorak question: Influence of the still size ?

by Oliver Klimek on August 17, 2009

Now here is a question that has been buzzing in my head for a while, and I have not found a statisfying answer to it yet.

We know that the shape of a pot still has a lot of influence on the distilled spirit. The still shape determines how aromatic components are separated from the water together with the alcohol and transported through the lyne arm and the condenser. It is also a well-known fact that copper is the best material for a still because it acts as a catalyst for favourable chemical reactions between the many substances that are present in the mash. So it is obvious that the still as a whole “does something” to the taste of the whisky.

It is also basic whisky knowledge that the size of a cask determines how quickly a whisky matures. The smaller the cask, the higher the ratio between surface and volume, so wood components and liquid remnants from the pores are diffusing into the whisky at a higher rate.

Now let’s combine these facts: Smaller stills have a higher ratio between surface and volume, so the catalytic reactions that happen during distillation should have a stronger influence on the spirit. Still sizes vary a lot between different distilleries. The Caol Ila spirit stills hava a volume of almost 30000 l whereas the Edradour still is just over 2000 l.

I am convinced that there is an influence, just because of the geometric fact. But how it can be nailed down escapes my grasp.

If you can shed light on this topic, please add a comment. If you know someone who could, please ask him.

{ 4 comments… read them below or add one }

alex April 16, 2011 at 12:45 pm

Chemical reactions have a huge range of rates at which they can occur, just sticking with the mention of cask aging (which obviously takes years) and distillation which is over much sooner you can get a sense of the scale. Personally I have no idea if these reactions occur at relatively slow rate or not.

I have heard someone say that a hot still will result increase the “grungeyness” you sometimes get with whisky. So the time spent in still is significant and hence increasing the surface area will probably likely increase the rate at which it happens, but it’s worth noting that increasing the size of the still will slow down the rate at which you can heat it generally.

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Markus Nilsson October 22, 2011 at 12:17 pm

I’m sure that the still size playes its part as you suspect, but the size is ony one variable. Unlike inside the cask, in the still it’s the -vapours- contact with the copper that’s essential, more than the liquid. This also means that a big still filled to 30% gives more copper contact to the vapours than a small still that’s filled as much as possible. Also at what speed/temperature you’re distilling affects this, so it’s not automatically less contact with bigger still, as with the cask comparison.

That’s my 2 cents!

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Jim Begg April 8, 2012 at 7:06 am

I understand that there is a legal requirement that stills used to make Scotch whisky have a minimum capacity of 40 gallons. Apparently experience has shown that stills below this size have insufficient boil space which tends to make them somewhat unstable. That said, my still has a 100 liter capacity and produces a great wee dram after only 10 months in mini casks.

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Oliver Klimek April 8, 2012 at 7:32 am

The legal minimum for commercial whisky production in the UK is 1800 litres. I have learned a bit since I wrote that. The higher surface to volume ratio of smaller (or narrower) stills means you get more copper contact resulting in more sulphur getting removed. In theory this should make the spirit lighter and fruitier. So making a Lagavulin clone from peated malt in your 100 litre still would probably not work.

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