Coming up for air

Having recently examined the mysteries of ‘old bottle effect’ (OBE) and heard from its opposing camps of sceptics and believers, Tom Bruce-Gardyne delves deeper into the bottle to explore this relationship between whisky and air

You can tell from the moment you step inside a warehouse filled with the sweet scent of wood and spirit that the interaction between the two clearly plays a big role in those long years of maturation. Those aromas are one side of the equation, the other being the air sucked in through the pores in the cask to replace the whisky lost to the angels’ share.

Those pesky angels are said to hoover up a staggering 29 million gallons a year in Scotland, and it seems their thirst extends even unto the bottle. “I’m looking at one on my shelf just now,” says the writer and rare whisky expert, Angus MacRaild. “It was probably bottled in the late 1950s and the level of the whisky in the bottle has gone down to around the mid-shoulder.

“So, it’s obviously lost about 5cm due to a very slow evaporation over the decades.” Angus may have been denied a dram’s worth of whisky, but he believes what’s left will have gained.

“It’s high strength at 104 proof which is just about 60% alcohol. So actually that process is beneficial in my view because the whisky has probably had the chance to open up nicely in the bottle with a bit of air,” he says. But alarm bells would have been ringing had it been a standard strength bottling. “At 40% or 43% abv, it’s much more likely that kind of evaporation would degrade the whisky,” he says. If left unchecked for another decade it might fall apart completely, leaving no more than perhaps the taste of soft, peaty water.

Angus MacRaild


Dr Andy Forrester, the Society’s spirits educator, isn’t wholly convinced by the idea that a whisky can improve with a bit of air if sufficiently strong. He imagines a half-full bottle sitting behind the bar. “That’s a lot of headspace in which to lose the volatile components, which is what flavour is in the main,” he says. “So, I think it’s perfectly understandable that you might see a loss of vibrancy of flavour.

“If the level is down to the shoulder and it’s spent 40 years in the bottle, the strength would have most likely dropped,” he continues. Ethanol, being one of the most volatile components in a whisky, is among the first to escape during maturation given our cool, damp climate. Whether this means it’s worth taking a hydrometer to the pub to check the strength of your dram, is another matter. One area where the two are in complete agreement is in how to resolve the half-open bottle conundrum.

As Angus puts it: “If you want to preserve the longevity of a whisky from a bottle that’s drinking great, and is in a wonderful, fresh condition, simply put it in a smaller sample bottle.”

With the headspace at a minimum, the risk of air damage effectively disappears.

ABOVE: The Thompson brothers in Dornoch


That’s fine for your own whisky at home, but it wouldn’t really work in the pub. At their famed Dornoch Castle whisky bar – a partner bar of the SMWS – the Thompson brothers have amassed an extraordinary collection of bottles, all of them open and available to try. The rarer, more expensive among them are given a squirt of argon every time a dram is poured. The inert gas, being heavier than air, sinks down to cover the whisky in a protective blanket.

Such preservation systems are well known in the wine trade, where backbars gleam with gas-powered, stainless-steel dispensers known as enomatic machines. But whisky is way more robust than fermented grape juice, and Simon Thompson wanted to test his theory. “I ran some experiments in the cellar to see if it was worthwhile,” he says. This involved pouring 50ml of a whisky into two standard bottles, one injected with gas, and then comparing them to the same whisky in a 50ml bottle after six months. “The one with argon was in significantly better condition, but not quite as good as the sample bottle,” he says, and you would imagine those differences would become more apparent over time.

Simon accepts Andy’s argument that any whisky exposed to air is likely to lose volatile elements regardless of its abv, but he believes a cask strength bottling simply contains more whisky to act as a buffer to the effects of air in the bottle than one diluted down to 40%. He also reckons that some whiskies will evolve more in the bottle than others, depending on how long they spent in the warehouse and how active the cask was.

Dr Andy Forrester


Angus MacRaild is particularly fond of old Society bottlings from the 1980s filled with “rocket fuel-strength whisky of well over 60% abv”, as he puts it. “Most have brilliant seals, but some have tiny flaws for whatever reason. I’ve had bottles where the whisky’s evaporated to almost below the label and they’re still perfectly fine. It’s the power of really young, cask strength whisky at play,” he says. “But some whiskies can really confound you. I’ve had bottles at 43%, sitting open for two years and they’re also just fine.”

However, Dr Andy Forrester, a self-confessed pragmatist, remains doubtful and wonders about the science to support these ideas. That said, he remembers years ago working in Oddbins where, among the whisky bottles opened to try was a Distiller’s Edition Cragganmore with just a dram left. “It didn’t have that kind of vibrancy, it had definitely lost something,” he says.

As for the mythical whisky bar with bottles dating back to 1900, his advice to anyone before choosing is: “Ask yourself what you’re buying – are you buying the experience of drinking something that was distilled before your grandparents went to war, or are you spending your money to get the best possible quality?” He wonders if the talk around OBE and air in bottles is somehow linked to an unconscious bias that whisky was better in the past. I suspect that’s a different story.