Let's Talk Direct Fired Stills [Discussion]

Hello again everyone,

Today I’ve got another vaguely interesting discussion post on direct fired stills. What are they? Why should I care? Does it make better whisky? All these questions and more will be answered!

First though, a lot more information can be found at the whisky science blog. This guy is much more professional than me (he uses references) and essentially, I’m just updating his list.

Much like maltings, having been onsite for many distilleries 100 years ago, direct fired stills would have been the norm. Back then they would have used a coal fire underneath the still as a heat source so that the alcoholic vapours would evaporate and could be collected.

Steam heated stills were introduced as early as 1887 to Glenmorangie, but many distilleries used direct fired stills until the 1950’s and 60’s when much of the industry was modernising (including the maltings).

A few distilleries stubbornly clung on though, and there is at least one distillery left that still direct fires all of its stills.

So, let’s talk a little about direct fired stills. What are they? Do they give a different flavour? If so, why?

 

To understand that, maybe it is useful to understand the other approach; steam.

The steam is generated in a steam boiler by natural gas or oil. The most common use of steam is the steam coil, where a coil of steel tubing inside the still is submerged in wash when the still is filled. The steam coil is pumped with hot steam to heat the wash and the rate of steam pumped through can be increased or decreased to change the temperature. The steam condenses in the pipes and returns to the boiler.

The other method is using steam cylinders or jackets, although these have now been outdated by the more modern steam coils. Whisky.com has some pictures of Linkwood and Glenlossie but I believe both these distilleries have been updated with new steam coils since these photos.

Quote from whisky.com on steam cylinders:

“Several of these hollow cylinders are placed inside the pot, standing upright. That way the wash can enter from below and leave heated at the top. The cylinders are double-walled so the hot steam enters the walls from above and runs down as condensed water. Small baffles between the thin walls of the cylinders lead the steam into a homogeneous flow in order to guarantee a constant heat emission. The steam is channelled through pipes at the top of the cylinders. Ring pipes collect the condensed water.”

I don’t believe there would be any difference in flavour between these three steam heating methods, other than efficiency and energy use perhaps.

Steam replaced direct fired stills for a number of reasons. Better heating efficiency, more control of heating, more even heating of the charge, optimising charge quantity and better heat transfer.

‘Direct Firing’ on the other hand is very different. It involves a direct flame to heat the still. Originally, all distilleries would have used coal or even peat to heat the stills. Nowadays, the EU have put regulations in place so that distilleries can no longer use coal but some still use natural gas or oil.

Because there are quite a few solids left over from the fermentation of the wash, these can burn to the bottom of the still and bring a ‘burnt’ or sulphury flavour through into the low wines. To stop this burning, direct fired stills will have a ‘rummager’ installed, which is a spinning contraption with sheets of copper chains to agitate the wash while it is distilling.

Also, the copper has to be much thicker on the bottom of direct fired stills. Partly because the rummager is going to scrape off some of the copper and partly to withstand the intense heating of the direct flame. The shape of the bottom of the still is also different, with direct fired stills the bottom of the still is concave to spread the heat of the fire more evenly. With steam heated stills it is the opposite, a convex shape giving more room for the bulky coils.

Glenfarclas is the only distillery
to direct fire all their stills

Similarly, the heat from direct firing is different to heating with steam, in that the heating with steam is very even and controllable. Whereas direct firing is uneven in its heating and less easily controlled. This might mean that over-frothing of wash stills is more common (called entrainment), burning of solids in the wash still even with a rummager and too fast or slow distillation of the spirit. It would be much easier to overcompensate with the heating (particularly with coal), turning the heat up, have it be too hot and turn it right down again to try and control it, see-sawing from one extreme to the other.

So, it’s uneven, harder to control and not as energy efficient. Why then do some distilleries stick by their direct fired stills?

Well, they’ve got some advantages too. For one, I would say (couldn’t find a reference but I’m sure others have said this too) that direct firing of stills is going to give you a more traditional tasting whisky. More substantial, more character and more flavour. Maybe not all good flavours, but those will mature with a long interaction with oxygen and wood (often good Sherry casks work best) to give you a better long aging whisky, à la old Macallan or any Glenfarclas, old Springbank, pre-closure Ardbeg, Karuizawa or pre-2005 Glendronach.

These whiskies tend to be able to age almost indefinitely, keeping their spirit character without being overwhelmed by oak, Sherry or oxygen.

Macallan stopped using their last direct fired still in 2010

Perhaps this is partly because of the partial cooking/burning of solids in a direct fired still, then removed by the rummager. This would allow any cooked or burnt flavour chemicals created to distill off into the spirit. The chemical associated with this phenomenon is Furfural, giving you a nutty or burnt flavour to the spirit. What this Furfural does during maturation is anyone’s guess…

(Of course, there are a tonne of other factors that go into the character of the whiskies I mentioned and direct fired stills is only one aspect.)

People say that ‘back in the good old days’ and ‘they don’t make whisky like this anymore.’ Well, it’s true, a lot has changed (more on that to come) but when did the direct firing of stills change?

Some very recently, Glendronach and Ardmore in particular changed recently and have had a hard time replicating their pre-steam stuff. Ardmore, I read, took months to change the cut points to a point where it was similar to the direct fired spirit.

Glenfarclas still direct fires all its stills, although other things have changed there in the meantime (Switching from wooden washbacks, and ummm no longer putting soap in the fermentations to stop the froth… Back in the 1980’s mind you). Glenfiddich and Macallan are the other distilleries well known for having direct fired stills, urrrrrr still.

Still House No. 2 at Glenfiddich

However, after some digging it may seem that Glenfiddich do not direct fire all their stills anymore (Source here says that only still house no. 2 uses direct fired stills. Which would be 13 stills out of 32. I think…), while Macallan may have stopped a while ago. I emailed both distilleries to clarify but only heard back from Macallan. I had seen sources say that Macallan stopped direct firing in 2002 and another said 2010. Both are correct in a way, Macallan started converting their stills to steam in the early 2000’s and finally finished in 2010. Their new distillery, which will be starting this year, will also use steam.

Other distilleries only direct fire their wash stills, for instance Springbank, Tobermory and Glen Garioch. This might be because any cooking/burning of solids could only occur in the wash still, as there are no solids in the low wines going into the spirit still. Therefore, the most difference to the final flavour of the spirit may come from the direct firing of the wash still.

Anyway, below is a small list of distilleries and when they stopped using direct fired stills. Of particular interest to me was Glen Grant and Glenlivet as older versions from this time and before are pretty available (although not cheap). Strathisla and Longmorn are two others that tend to fly under the radar, and stuff from their direct fired stocks are available.

Direct Fired-

Glenfarclas (All stills)

Glenfiddich (13 stills of 32)

Springbank (Wash still only)

Tobermory (Wash still only)

Glen Garioch (Wash still only) (1995 spirit still)

Macallan (2010)

Glendronach (2005)

Ardmore (2001)

Longmorn (1994)

Strathisla (1992)

Ardbeg (1989 wash, 2001 spirit)

Glen Grant (1986)

Glenlivet (1986)

Caol Ila (1974)

Thanks for reading!

Let me know what you think! Does direct firing of stills make a difference? Do you like the flavours from direct fired whisky? Do you drink nothing but the finest Golden Promise, pre-war, direct fired Macallan? Do you give a shit? Let me know!