Monday 14 August 2017

Let's Talk Partial Triple Distillation: Your Guide to Springbank, Mortlach & Benrinnes

Hi everyone,

So today I’ve got another one of those random things that has really interested me and I wanted to learn more about. So, I did and then I wrote something about it. This time around it’s partial triple distillation. That magical, nonsensical redistilling of seemingly random parts of the spirit that give you the wonderful whiskies of Springbank, Mortlach and Benrinnes.
So let’s talk a bit about this process and try to make sense of why they do it and what effect it’ll have on the whisky. 

To try and understand partial triple distillation it may be an idea to try and get our heads round double distillation first, then triple.

A double distillation is the simplest. You have two pot stills, mainly because the distillate from one still can only produce an alcohol of about 45-50%abv and there are a lot of solids in the wash that should be separated first. You put the wash into the first still at about 8%abv and heat it, the alcoholic vapours evaporate and you get a spirit coming off at about 45-50%abv. You keep distilling and the abv drops and keeps dropping, all the way to 1%abv. At this point the wash has an abv of 0.1%abv and isn’t worth distilling any further.
What is in the collection tank is called the low wines and should be about 23%abv.
You want to distil this a second time to make it purer again and collect the parts of the spirit you want. So, you put the low wines in a second, normally slightly smaller still, and heat it up again. The alcoholic vapours rise off again, this time about 75%abv but contain a lot of Methanol but also fusel oils from the previous distillation. You let the Methanol and fusel oils leave the system in the Foreshots but you keep them because they contain a lot of alcohol.
After 5-30 minutes, the spirit is good to go and you start collecting it. This is the Heart and contains the good stuff.
Once the spirit drops below a certain abv, the Heart is finished and the Feints start. The later parts of the distillation contain ‘heavier’ oils and flavour chemicals and the later the cut to Feints, the more of these will be included. So, the tighter the cut, the lighter the spirit should be. A longer heart cut should result in a ‘heavier’ spirit. The Feints are the final part of the distillation, let say from the end of the heart 70-62%abv to 1%abv, again, at which point what’s left in the still is at 0.1%abv and isn’t worth distilling.
Still with me I hope.

The Wash & Feints still at Springbank
Triple distillation involves three stills (Duh) but can be done a bit differently, because you’ve got more cuts to play around with. For instance, Auchentoshan triple distil differently to Springbank’s Hazelburn because they want a tighter cut and a higher strength of alcohol, giving you a lighter spirit.
At Auchentoshan, the spirit from the second distillation is cut into 70-20%abv that goes into the third still, and 20-1%abv goes back into the second still. Whereas, at Springbank’s triple distilled Hazelburn, they take everything from the second distillation and put it into the third still. Auchentoshan take a very tight cut from the spirit still, giving them a final abv of just over 80%, but Hazelburn is only 72-3%abv. In general though, these triple distillation systems are reasonably simple. You have three stills, you distil the spirit three times to get a greater purity, a lighter spirit and more copper interaction.

But what if you wanted more copper interaction, but a heavier spirit? Then you get to this grey zone of partial triple distillation. It isn’t three, it isn’t two. It’s something in between.
It’s a practice that has produced Springbank, Mortlach and Benrinnes for years. Making these some of the best whiskies in the world. Ralfy’s highest score went to a Mortlach from Signatory, I think his second highest to a Springbank. Also, loads of people rave on r/Scotch about that Benrinnes 23.
These whiskies are known to age really well in the long term, especially in Sherry casks, giving you very rich, full bodied whiskies that cam keep their spirit character without getting overwhelmed by oak or Sherry. It helps that Mortlach and Benrinnes also use Worm Tub condensers.
So, what is going on here?
How do they do it?

Well, what it usually involves is distilling a part of your distillate three (or even four) times and part of it twice. Giving you something in between two and three. The problem with trying to wrap your head around it, is that every system is slightly different. Luckily for us there are only three, so let’s start with Springbank.

At Springbank there are three stills. The wash still is direct fired (more on that here) but the first distillation is normal, the wash is heated and 20-25%abv low wines is collected. Most of this low wines goes into a ‘Feints’ still, which is the second still of the three. This is distilled a second time and no cuts are taken, giving you a Feints spirit that is probably just under 30%abv. This is combined with the Foreshots and Feints of the previous distillation from the third still, making the final abv in the Feints tank 30-35%abv. They then put 80% of that spirit into the final still of the three, along with 20% of the low wines from the first distillation. This is distilled and Foreshots, Heart and Feints cuts are made as usual, giving a final abv of 71-72%.
In the industry, a distillation without cut points in normally called a blank run, and this is what Springbank are doing with their second distillation with Springbank and Hazelburn. What this means is that the spirit from that distillation hasn’t really been purified or had any of the flavour chemicals or oils separated, but it would increase copper contact and heat related reactions within that part of the spirit. Some solids are also left over in the still at the end, I believe, with a small amount of water.

This process is a little more complex for Benrinnes.
Benrinnes has six stills that work in two pairs of three. Again, there is a wash still, a ‘Feints’ stills and a spirit still. For their distillation process they take cuts from every still, this means taking what they term ‘strong’ and ‘weak’ feints from the first and second still.
The first distillation in the wash still has two cuts, essentially the first cut is a combination of the Foreshots and Heart and is termed ‘strong Feints,’ the last part of the distillation is termed the ‘weak Feints,’ but essentially… Feints.
Alright. So, the strong Feints go into the third still (the spirit still) and are distilled in that, while the weak Feints go into the Feints still. Cuts are taken from both. Again, from the Feints still, strong Feints (Foreshots + Heart) are taken forward to the third still, while the weak Feints go back into the Feints still to be redistilled. Confused yet? The third and final still (the spirit still) has four cut points; Foreshots, Heart, strong Feints and weak Feints. I know, I know but let’s keep at it. The Foreshots and strong Feints go back into the same still (the spirit still, the third one) to be redistilled. Meanwhile the heart is taken as the spirit and the weak Feints go back a stage to the second still (the Feints still). Phew This leaves us with spirit of about 67%abv. Got it?
What are you doing to my mind and why does it make a difference?
Well, this redistilling of the weak Feints in this extra still is, again, increasing the copper contact and heat based reactions. How does it differ to Springbank. I would say these effects would be enhanced by this complicated process, and also by their use of worm tub condensers.
Benrinnes started this distillation system in 1974 but stopped in 2007. Anything distilled after 2007 will have been double distilled, although I believe they have kept the worm tubs.

Well, now we get to the most complicated of all: Mortlach.
Mortlach is very special. Like Benrinnes, it has six still but one of these is very special. So special that is has a special name. The Wee Witchie. This special still does special distillation runs that are… um, special.
Instead of working in threes, the stills at Mortlach work more in pairs. One pair is separate from the other four in that it just produces double distilled spirit. The other four are the complicated ones. You have two normal wash stills, a normal spirit still and the Wee Witchie (essentially another Feints still, but much smaller than the other stills at Mortlach). The first 80% of the low wines from both the wash still distillation runs go into the normal spirit still (we’ll called that the High Wines), while the last 20% of the low wines from both wash stills goes into the Wee Witchie (I’m going to call that the Low low wines).
The High Wines that go into the spirit still are distilled as normal with a Foreshots, Heart and Feints cut with the Foreshots and Feints going back into the same still to be redistilled and the heart taken as spirit. All of that is just double distilled spirit.
Ok, fairly simply so far. The Wee Witchie meanwhile, has the Low low wines from the wash still distillations (the last 20%). This is then distilled in the Wee Witchie with no cuts taken (a blank run, you’ll remember), with only the solids removed in between. This spirit is then redistilled in the Wee Witchie a second time, again with no cuts. Then, they redistil this spirit in the Wee Witchie a third time, this final time they take Foreshots, Heart and Feints cuts, with the Foreshots and Feints going back into the next Wee Witchie distillation and the Heart taken as spirit to be mixed with the spirit from the other two spirit stills (although I wish we knew the cut points of the Wee Witchie, and the other stills). This gives you a final abv of around 71-72%.
‘What the actual fuck?’ You might be asking. Yeah, quite.
Mortlach claim that this distillation regime means that their spirit is 2.81 times distilled but I think this figure is slightly meaningless. To me, more distillations implies greater purity and a lighter spirit but Mortlach’s practice here does exactly the opposite. If anything, it isn’t even partial triple distilled, it’s partial quadruple distilled.

So, what exactly are those blank runs in the Wee Witchie doing?
Well, again remember that this unique distillation practice is only part of the picture and that there are loads of other factors, one of the main ones being that they also use worm tubs. Also remember though, because the Wee Witchie is really small and Mortlach run their stills fast and worm tubs cold, with no air rests to rejuvenate the copper (Source) it means that the copper contact from these blank runs is very little and one of the main heat based reactions is between sulphur and copper.
Well, what it seems this process does in practice is let a substantial amount of sulphury and meaty flavours into the final whisky.
Hold on, was this Mortlach or a urine sample?
Why? To be honest, I have no idea (I’m no chemist) but that seems to be the consensus and also my experience of their spirit. When I asked a friend who is a chemist, he was stumped too but did give an insight to a possibility. If the Wee Witchie is removing very small amounts of sulphur, from its small size, fast distillation and cold worm tubs, then the level of sulphur compounds may decease very little, while the volume of liquid in the charges is decreasing from successive distillations (albeit with no cuts). This may mean that the sulphur levels are staying around the same in these distillations but the concentration relative to the volume is going up. Remember that the Low low wines going into the Wee Witchie will be a much lower strength than normal low wines that would go into a normal spirit still, and therefore may contain more ‘heavier’ flavour compounds, including sulphur, from the wash. As I said, it’s a possibility. Maybe someone more technically minded can offer another explanation?

Overall, it seems that these strange distillation systems that go between two and three distillations definitely give their own style to the whisky. In particular, Springbank, Mortlach and Benrinnes all seem ‘heavier’ in character than many other malts. They also work well with intense Sherry casks and longer maturation in them. For me, as I said with direct fired stills, it’s something that isn’t going to give you the best flavours in the world getting off the still (Charles MacLean says he doesn’t like young Springbank: Source), but gives you flavours that are going to mature and oxidise over a longer time into something really wonderful.

Below is the list of those that use these partial triple distillation systems:

Partial Triple Distillation

Benrinnes (1974-2007)

What do you think? Do you like Springbank (Who doesn’t?!)? Have you tried a sulphury Mortlach or Benrinnes? Do you think these partial triple distillations matter at all? Did you enjoy reading this, or did your brain explode? Let me know!!

1 comment:

  1. Great article, very interesting!
    About Springbank, there may be a small inconsistency: you mention in the text that there is no cut in the distillation that happens in the feints still (or intermediate still). Yet on your schema there is an arrow named "feints" that goes out of the intermediate still and goes back to it, implying that there is a cut. I think this arrow is a mistake, or maybe I misunderstood?