Production

Mash Tun Time Machine

Boann Distillery in Ireland is bringing lost mash bills back to the future
By Mark Jennings
A cask of maturing Boann spirit
A cask of maturing Boann spirit
At the start of the 19th century there were more than 100 licensed whiskey distilleries operating in Ireland, all with their own mash bills (the ratios and types of grain used to make spirit – typically malted and unmalted barley, oats, wheat, or rye.)

When the industry reached the depths of its decline in the 20th century, only two Irish distilleries remained, each making just a handful of whiskey styles. Gone were the oats, wheat and rye. The dynamic variety that Irish whiskey had been known for was quelled forever, or so it seemed.

Out of the blue, one man made it his mission to track down as many of these extinct mash bills as possible, and a distillery gave him the chance to resurrect these ghosts as drinkable whiskey. Fionnán O’Connor was a student of medieval literature and history at Trinity College, Dublin, when his passion for Irish whiskey began to take over his life. Perhaps it was the time living abroad for his research, in San Francisco or Florence, that made him seek the story of his home spirit, but whatever it was, it bit him deeply.

From teaching classes on whiskey at UC Berkeley’s Celtic Studies department, to running seminars at San Francisco’s legendary cocktail bar Bourbon & Branch, his brain was whirring, and the result was one of the first modern books on Irish whiskey, A Glass Apart: Irish Single Pot Still Whiskey (2015). This creative endeavour might have been enough for the average scholar, but as his reputation grew in whiskey circles, O’Connor suddenly found his academic interest in the spirit subsuming his passion, as in 2018 he began a PhD focussed on ‘The History and Culinary Potential of Lost Irish Mash Bills’ with the Technological University of Dublin.

“There was a lot of stuff left over from the book; people knew that oats were used once upon a time, but there wasn’t a lot out there as to the scale or even ‘the why’ – the PhD sprung about through that,” says O’Connor.
Fionnán O’Connor

If ever a PhD thesis could be hotly anticipated, this would be it. O’Connor has been sharing his findings as he discovers them, with his work exciting whiskey fans and distillers alike. The process has taken him deep into Irish whiskey’s illustrious but often forgotten history, leading him to become part of the submission to redefine what can actually be called Irish whiskey, and, more intruigingly, to discover a trove of lost mash bills from long-closed Irish distilleries, dating back to the early 1800s. At that time, there was far more flavour diversity in whiskey than we have today, due to regional availability of grains and drinkers’ preferences.

O’Connor feels the most fascinating thing he’s discovered is that, in his words, the official stories of Irish whiskey are “incorrect or just gross simplifications.” One such story that abides is the tale that the unique pot still style (of mixing malted and unmalted barley) came about because of a canny attempt by the Irish to skirt the Malt Tax of 1785. However, O’Connor uncovered records showing significant use of unmalted barley 80 years prior, on such a scale that the Maltsters Guild petitioned Parliament to put a tax on unmalted barley, to compel people to use malt. “I found myself having to break down these concepts, scrapping modern ideas of what whiskey is supposed to be,” adds O’Connor.

Of the many areas his research touched, it was the discovery of lost mash bills that has set the heather alight for Ireland’s nascent distillers; all are eager to taste something from their history, or use these bills to create innovative new products with a heavy nod to the past. These discoveries are what O’Connor is most known for.

“In the archives you can spend five days and find nothing, and then, in one day, in five minutes you find gold,” explains O’Connor, whose prior academic experience came in handy when hunting for the old recipes. Though several of these were there for easy finding, some required long days sifting through records, like the Old Comber bill (1825–1953), which was eventually found in the Public Records office of Northern Ireland. “I remember finding information about Comber in the catalogue and excitedly going to the desk, but they just couldn’t find it. I went back to doing something else, dejected. Suddenly a massive box appeared…and it was there.”

However, discovering these mash bills was only part of the adventure. O’Connor knew he had to have them made and distilled to really experience and understand how the distinct grain types contributed to the profile of each whiskey. To achieve this, O’Connor needed a very specific set up: a distillery that was triple distilling – specifically, one using large, bulbous stills – with a mechanised system of enough precision to take consistent spirit cuts, to ensure a control across all distillations. Matt Healey, global export sales manager at Boann Distillery, heard about the project and, with the help of head distiller Michael Walsh, convinced the owners to take it on.
Adverts from the 19th century advertising mixed mash bills

Located 50 miles north of Dublin, Boann was ideally suited to the project. Built specifically to make pot still whiskey, it’s equipped with kit such as a mash conversion vessel, which allows Walsh and his team to mash in the grains at a set temperature and raise it through various temperatures with a high degree of control – something that’s extremely important for brewing oats. Walsh explains that, as is the case with porridge, it is easy to make a “big gloopy mess” without taking due care.

Boann’s stills use new ‘nanocopper’ technology, giving the inside of the neck an uneven surface, which quadruples the copper contact area and therefore can deliver a cleaner distillate running off the still. This gives Walsh more freedom, in terms of both spirit quality and flavour, which was crucial for the vintage mash bills project, where there was a worry about low yield from some of the bills. To underscore how complicated this experiment was: Boann’s brew kit supplier refused to offer support for the project, so sure was the company that the oats would
be impossible to distil. Thankfully, it was wrong.

The Boann team began distilling in late 2020, choosing 10 vintage mash bills. Walsh admits that a little reinterpretation was required. Some of the distilleries had been double (not triple) distilling, and, of course, there was no way to know how heavy or light each distillery’s distillate was when the bill was written down, or the fermentation time and method, or the cask types used to mature the spirit. Walsh’s aim wasn’t to recreate the exact spirit of the past, but more to use the variance in these bills to make distinct distillates in a controlled manner for scientific research; specifically, he hoped to understand what impact the ratio of each ingredient has on the overall profile of the spirit.
Boann’s head distiller, Michael Walsh, and O’Connor

“We had to approach it from a scientific point of view, with every single parameter consistent … the amount of water that we used in the mashing process, the temperature of the water, the amount of time it spent at each temperature – each was identical, irrespective of how the original distillery would have done it,” says Walsh. This presented the team with a massive challenge: to plan everything in detail in advance and ensure the results stood up to academic rigour. Walsh admits that this was not his usual process when making a new whiskey: “I’m more of a dive-in-with-both-feet guy, and we’ll see how we get on.”

“The oats were the biggest surprise; I expected something muddy or heavy or creamy, but they ended up tasting really sweet, specifically vanilla-sweet,” enthused O’Connor. His favourite bill is Mash 10, which he calls his ‘darling.’ This fondness isn’t just on account of its flavour, but because the bill was derived from a 1920s Locke’s Distillery bill, the discovery of which was his first big research breakthrough. It’s made from 40 per cent unmalted barley, 40 per cent malted barley, 15 per cent oats and 5 per cent rye. Together, they deliver a crunchy biscuit palate, which morphs into lemon sherbet, then sour fruits, with a strong, sweet pink apple finish.
Michael Walsh, managing director Pat Cooney, and Fionnán O’Connor

For Walsh, it was just making the spirit after years of discussion that most excited him: “I have spoken at great length over the years to Fionnán about what we should be doing as an industry and what grains belong in a mash bill... it’s all grand to be talking about it and have your theories, but to actually get to do it – that has been brilliant.”

In total, Boann distilled 2000 litres of pure alcohol from each bill, and this went into four different cask types: ex-sherry and rum, as a nod to the past, and more modern ex-bourbon barrels. The team have also filled what they call ‘New Era of Oak’ casks, which are shaved and re-toasted Bordeaux wine barriques from ASC Cooperage in France. What’s more, O’Connor was not paid for this project, nor made any commission or the like, to ensure the validity of the research is untainted.

This project makes corporeal the rich history of Irish whiskey for a new age. It charts not just the story of regional innovation and variation, then nationwide stabilisation into a few core mash bills, signalling the late 20th century’s descent into homogeneity, but is much more than this rather sad tale. This research has already proven to be a catalyst for distillers to create their own versions of these lost bills, and it has challenged, and looks likely to change, the very definition of what can be called Irish pot still whiskey.

“Many people know the story of Irish distilling’s rise and collapse, but the story of the lost tastes and aromas, the knowledge that most of those whiskies were different to ours, comes as news to most people,” concludes O’Connor. Whisky drinkers will soon be able to taste that history for themselves.