Boulder Spirits: the art of making good single malt whiskey in the USA

Blog post by Henrik Brandt

Late last year I got the chance to meet the man behind the company when he visited Copenhagen. It is remarkably rare for an American master distiller to drop by our small country, so when I was asked whether I wanted to interview Alastair Brogan, I said YES immediately. He calls himself "Chieftain", but he is a master distiller.

It turned into a proper geek-out, and you can read about some of the things that make Boulder special in this post. I also recently got to taste a sample from the cask Whisky.dk has selected for Whiskymessen 2024, and you can read my verdict on that cask at the end.

So who is Boulder Spirits? An American producer unlike most others. First, they are in Boulder, Colorado, and although the state now has a fair number of distilleries, it is certainly not every day you hear about new producers there. Second, their master distiller is Scottish, with a focus on single malt.

American Single Malt (ASM) has been produced for a good few years now but still has no classification of its own. I think it will happen this year, though, and it really should have happened in 2023. There is a very active and fairly large group calling itself the "American Single Malt Whiskey Commission" (ASMWC) working to get the classification over the line, and you can read more about them here: https://www.americansinglemaltwhiskey.org/

Master distiller Alastair Brogan

Boulder Spirits has focused on single malt from day one, but also makes bourbon. Their bourbon is made with a rather unusual mash bill, using a full 44% malted barley. That is 5-10 times more than most other producers. Asked directly why he had chosen so much barley for his bourbon, Alastair answered that he loved working with this particular grain, and that he preferred its ability to form the enzyme amylase. Amylase converts starch into glucose, which the yeast cells need in order to make alcohol. That high a concentration of malted barley gives their bourbon a unique flavour - and as mentioned, you can read more about that via the link at the start of this post.

Boulder Spirits' core range

ASM products are basically made in a way that closely resembles single malt in Scotland, but there are a couple of differences:

New casks are always used. Producers are rather pleased with that, because it gives them control of the maturation from the very start. They do also re-rack into used casks - at the time of writing Boulder has expressions that have sat in both sherry and port casks.
Almost all malt is dried with hot air, and smoke is used only very rarely. Boulder does have a single peated product in the portfolio, but that is not where their focus lies, and the same goes for nearly all the other ASM producers.
Almost all products carry no age statement (NAS), and there is generally no focus on making products matured for many years. When you start with new casks and summer temperatures run high, you also have to be careful they do not sit too long.
Distillation runs to a maximum of 80% ABV, and the whiskey never goes into the barrel above 62.5%.

Beyond these points, making ASM is not sharply different from Scotch single malt. ASM must of course be produced and distilled in the USA, and once the official certification lands, ASM and bourbon will be the only ones of the many American whiskey types that MUST be produced and distilled in the USA.
As mentioned, my conversation with Alastair went into geek mode fairly quickly, because I was especially keen to understand what makes them special in a country that now has more than 1,000 distilleries. And as the conversation went on it became clear that Boulder - and Alastair in particular - has a very good idea about this.

Here are a few interesting things I managed to pull out of him that you will not find on their website:
The process before the spirit goes into the barrel: they have gone to considerable lengths to make sure the water they use is of good quality and, not least, contains a minimum of iron. They have also deliberately chosen pot stills, despite there being far better economics in a column still. Even though they have little experience with column stills, Alastair was firmly convinced that pot stills are essential to achieving the flavour profile they want. The spirit ends up around 70-75% ABV and is cut back to 60% before going into barrel. They also have an experiment running at 52.5%, and will evaluate whether that is the right road once the whiskey is ready. The alcohol level at the start of maturation is called barrel entry proof, and a low figure is better than a high one - though it also costs more money.

The choice of barrels: they use new American white oak. Although the ASMWC does not specify this as a requirement, a small technicality means all ASM producers do it anyway, because there is a whiskey type in the USA called malt whiskey where new casks ARE required. Boulder has also chosen to toast their barrels for 75 minutes before the inside is charred for around 45 seconds to what is called char level 3. They use ordinary 53-gallon barrels (200 litres), but tried small 15-gallon barrels (57 litres) early on to accelerate maturation. It did not work for them, and as Alastair put it: "It seems to be difficult to cheat Mother Nature." All their barrels come from Kelvin Cooperage in Kentucky, which I have visited myself, and which is probably one of the best coopers in the world.

Before the whiskey is bottled: they do not chill filter, which is a little unusual (but good), since most of their products are 46% ABV. Whiskey below 47% can go cloudy or slightly hazy if it is chilled hard, for instance in transit. That problem is solved by chill filtering. Chill filtering can also strip some of the flavour, so it is impressive that they have opted out. They have also started experimenting more with cask strength products so drinkers get to taste the unadulterated thing. The cask strength product currently sold in the USA is 66.87% ABV.

Overall: all of this tells me the focus is on quality, and that they are doing all the right things to get there. They think about pretty much every stage of production, and they have a clear plan when it comes to setting themselves apart. I have tasted their entire core range and it is my firm view that this focus is reflected in the quality. I was very sceptical myself before tasting their bourbon with so much malted barley in it, but I ended up filing it under "Fantastic".

But what about the expression made specially for Whiskymessen? Let me finish with some quick tasting notes:

Boulder Spirits American Single Malt Single Barrel (#1216).

Matured at least 6 years. 50.5% ABV.
Nose: Lovely sweetness and very balanced alcohol. I catch both vanilla and caramel straight away, and that is certainly down to the new casks. The malt is a little subdued at first but comes forward bit by bit. No smoke.
Palate: "Yum" is the first impression, and I have made friends with it almost before it hits the tongue. Really good mouthfeel, and the malt now steps clearly forward. Lovely sweetness that harmonises well with the rest.
Finish: Very pleasant and with good length.
Conclusion: A really lovely whiskey and one of the best American single malts I have tasted. On pure quality it gets 89 points, and sneaks all the way up to 91 when the price is taken into account. A clear recommendation from me.

P.S.: If you have run into new terms in this post, there is an overview of the specialised American terminology at https://straightwhiskey.dk/forkortelser-og-fagudtryk/. If you prefer explanations on video, you can find detailed ones on my English blog https://thebourbonnerd.com