How to distil and cask high quality whisky
Interview with
The last part of the whisky making process is concentrating the fermented wash into the final blend, ready for casking...
Chris - Wow. You’ve got the best view in Scotland, I reckon.
Alistair - Yeah, it’s a still house with a view, isn’t it? You’ve got this glass box around the still that gives it a kind of greenhouse effect. The guys in production have got the best office in the city at the moment.
Chris - They sure have. Before we talk about these two enormous stills in front of us, can you just tell us a bit about the history of this building and where we are? How did you come to be literally on the dockside of the Clyde in the middle of Glasgow?
Alistair - Yeah, so the building to the right of us here is actually an old pump house. It’s a hydraulic water pump, and its job was to open and close a hydraulic bridge, basically allowing access for ships exporting all over the world. We had the Queen’s Dock that opened in 1877, and probably a lot of the exports from the city—and whisky being one of these main exports—were being controlled by this very building that we’re standing in at the moment.
Chris - We’ve admired the view, but the dominant feature in this... I want to call it a room, but it’s like a giant conservatory, tens of metres tall, with these two enormous copper stills.
Alistair - Yeah. So this is where the distillation process happens. The fermented wash that we spoke about in the tun room and the fermentation washback gets pumped through into this big copper still. This is just like a big copper kettle, and it’s got a heating element in the bottom. If you try to describe the shape, it’s an onion-shaped still, and halfway up the neck of the onion is a sight glass. You can see the liquid dancing in the window there, boiling away. What we’re doing is capturing the vapours coming off the top of the still, through the swan neck, and condensing them back into an alcohol liquid—a distillate. This runs into this brass box you see in the middle of the still house, which we call the spirit safe. The spirit safe is important because it allows you to see the liquid running, the rate it’s running at, and also to sample the alcohol strength and temperature of the spirit, which is very important to us.
Chris - What about the stuff that we don’t want to come across? There must be some bits of yeast in there, and also, are there any chemicals that you don’t want to distil across? How do you get rid of those so that you just get good quality spirit?
Alistair - Yeah. Firstly, on the solids—you’ve got the yeast, the dead yeast cells, and some fines that may have come through from the mashing process. But as you can see, the liquid is only halfway up the neck of the still as it’s boiling, so no solids are getting above that. Only the vapours come off the top, moving onto the spirit distillation. All the spirit you collect from the wash still gets pumped into the next still, which looks similar. The difference is you’ll see there’s a ball in the middle of this one—a copper ball. What we’re doing here is boiling up using the exact same process, but this time there are some unwanted characteristics and flavour compounds we want to discard. This happens at the early stages of the still. We discard that back into the previous tank for the first 15 minutes. We call this term the ‘foreshots.’ After the foreshots, we start collecting a new-make spirit at a strength of 76.5% alcohol. Here at Clydeside, we’re trying to create a delicate, clean new-make character. So from 76.5% down to 71%, that’s our final new-make spirit, which goes into what we call the ISR—the Intermediate Spirit Receiver. Then it’s pumped to the filling store for tanking offsite.
Chris - You distil it once, collect everything, and then put what you collect into the next distillation tank and distil it again. But you put back the first 15 minutes of what comes off into that tank so that you don’t get those characteristics going into the final blend. And what comes off that second distillation is that 76% down to 71% alcohol, which is going to become the final product.
Alistair - Yeah, that’s correct. And it’s not just the distillation part of the process—it’s all parts. You’ve got the mashing, you’ve got the clear worts, you’ve got the dried yeast, the type of yeast... There are a lot of variables in there that contribute to the final whisky.
Chris - And presumably the stage we haven’t yet discussed, which is that it leaves here and goes into casks. Tell us about that.
Alistair - It looks like the most boring part of the process, to be honest—the casks sitting in a warehouse for most of their life. But I would say in the region of 70% of the flavour of all whiskies comes at this part of the process. So you can do all the mashing, fermentation, and distillation, but depending on the quality of the wood—and it’s all about the wood—what’s it been used for? Has it been sherry? Has it been wine? Has it been bourbon? The time you store it... There are a lot of reactions going on.
Chris - These are second-hand casks. What’s been in those casks before is an informed judgement that will influence, or directly lead to, a characteristic in the product.
Alistair - Yes, we predominantly use bourbon casks here.
Chris - Are you going to show me some of the product?
Alistair - Absolutely, yeah. That’s the best part of today—getting the chance to go and have a nose and taste some of the final matured whiskies. Okay, so this is the new-make spirit. You can see it’s crystal clear—no colour whatsoever. This is the spirit that’s just come off the still, reduced to 63.5% and ready to go into the cask. But this is your chance to try the new-make spirit. It’s totally clear; it looks like water.
Chris - I would say that it looks like gin, doesn’t it? Let me have a sniff of it. Yeah, I mean, it smells like the classroom or lab ethanol bottle. Okay, I’m going to try it... There’s a lot of flavour to it. You can taste the barley.
Alistair - You get a kind of malt-biscuity note at the beginning, but once you get into it, you start to get more of the fruity flavours from the fermentation. So you’ve got more of a tropical fruit profile. Add a touch of water to it as well.
Chris - Is that what one is supposed to do with whisky? Because there seem to be mixed views on whether or not one should add water.
Alistair - Drink it how you like it, is the answer to that. The industry rule of thumb is that if it’s a cask-strength whisky, a touch of water takes that sharpness, that burning edge off and opens up the flavours. So, you’ve tried the new-make spirit. Now let’s move on to something a wee bit more enjoyable, I suppose.
Chris - This is now going to have the characteristic of the cask effect in it, isn’t it? Because this has been in a cask for a period of time. So whatever was in there before has now been imparted to it. Is this from a bourbon cask, then? Because it’s quite pale.
Alistair - This is actually our first release, and it’s from two casks, believe it or not—a bourbon cask and a sherry cask.
Chris - This is very smooth. The other one was quite powerful—obviously it was a lot stronger—but this is very, very smooth. It’s sort of velvety, slides around your mouth, and it’s very soft and delicate.
Alistair - Yeah, it has a really nice delicate mouthfeel and a nice oiliness. This has been aged just over five years, reduced from 63.5% down to 46%.
Chris - So you age it at high strength and then dilute it. You don’t dilute it and then start the ageing in the casks?
Alistair - No, we dilute it down to 63.5%. That’s the industry standard, which is higher than the bottle strength, as you rightly say, and we mature it at that strength. The reason you don’t go lower is that year on year, you’re losing alcohol strength, and you don’t want to get down below 40%.
Chris - Do you know what amazed me? When I read about the fraction of food and drink exports from the UK that Scotch makes up as a proportion of the industry, it’s a huge share. It’s more than a fifth, isn’t it, of our exports?
Alistair - Yeah, I believe so. I don’t know the current figures today, but recently, single malt whisky made up 25% of all food and drink exports from the UK.
Chris - Well, I’ve got to hand it to you, Alistair—thank you so much. I’ve learned so much from you in the last hour or so of looking at this process. I thought I knew basically what went into this, but I had no idea. So thank you for giving me the insights and for showing me the product going from grains of malted barley to emerging as something that’s firewater, and then with the cask, it tastes delicious. It’s been a real treat—thank you.
Alistair - It’s been a pleasure to take you through a quick journey of the processes. Thank you very much for your time, and hopefully your listeners will come and see us here the next time they’re in Glasgow to enjoy the same experience you’ve had.
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