“I’ve gone through the rollercoaster of loving smoky and peated whisky, to loving Speyside, to loving coastal, and back to smoky whiskies,” says Jay Cozma, general manager of Sydney’s spirit-haven Baxter Inn. “It’s a constant journey. Which is cool.”

Whisky also has to go on a journey: ageing. From grain to bottle, time is a crucial factor in what a whisky will become. We asked Cozma to explain the steps along the way.

The barrel
When first distilled, whisky is a clear, highly alcoholic liquid called “new make spirit”.

“There’ll be slight flavours to a new make depending on how it’s produced, where it’s produced and the effects the still has on it,” says Cozma. New make spirit only becomes whisky when it goes into an oak cask. Scottish law demands at least three years of ageing.

“Sixty per cent of the flavour characteristics you’re experiencing are coming from the casks themselves,” he says. This means the type of wood and size of the barrel a whisky goes into will be a determining factor in how it tastes. “As whisky goes into the casks, it starts interacting with the wood. You get a lot of sweetness coming off the oak, and those characteristics in the spirit allow it to mellow.”

The most common choice of wood for Scotch whisky is a cask that previously held bourbon. But sherry and port barrels can be popular choices too.

Temperature
Once a whisky is in its barrel, it’s not completely sealed off from the world. Its surrounding environment still plays a role in how it ages and, ultimately, how it tastes.

Even within Scotland, there’s plenty of variation, from the Highlands and Islands up north, to Speyside in the middle of the Highlands, then Lowlands, Islay and Campbeltown rounding out the south. “If you’re looking at the highlands compared to the lowlands, you’re going to have different humidity, climate, [and] impacts of the weather,” says Cozma. Temperatures and humidity can affect the taste because wooden casks allow for evaporation. In areas of high humidity, the whisky can even evaporate. Distillers call it the “angel’s share”.

“You might come back in 10, 15, 20 years and find you’ve only got 30 per cent of that whisky left,” says Cozma. But because parts of Scotland have relatively constant temperatures, it allows whiskies to successfully age over a long period of time.

Time
The barrel and ageing temperature both play a role in the potential flavours of a whisky. The determining factor is time. “With a spirit aged for 10 years as opposed to 18, you’ve got a greater amount of time the spirit is interacting with the cask,” says Cozma. “It’s resting, it’s maturing, it’s mellowing. It’s taking those vanillas, fruit notes and oak characteristics into the spirit itself.”

The age on a bottle is the minimum age statement. Alternatively, whiskies without an age listed are when Master Distillers blend young and old whiskies together to create a variation or unique flavour profile. Although there are plenty of subtle variables (even identical casks in different spots in a warehouse can turn out differently), it essentially comes down to this: the longer a whisky is aged, the richer the flavours will be.

Choice
Just like wine, many people assume the older the better when it comes to whisky – but it’s not necessarily a rule. For example while The Glen Grant did recently launch a non-age statement drop in Arboralis, Cozma says starting with a flagship product like its 10-year-old single malt is a good way to get a representation of what the distillery can do. “Their flagship product is the one they stand behind the most, it’s the iconic product for that brand,” he says. Then if you like it, you can move onto something richer. For example Cozma says Glen Grant’s 18-year-old whisky will introduce a range of new flavours: “You want vanilla, light nuts, light caramel and rich oak to come through in [the] 18-year-old whisky.”

Cozma’s advice for sampling whisky remains the same, regardless of how many years it’s spent ageing. “The only wrong way to drink a whisky is the way you don’t enjoy it,” he says. “Whether that’s in a cocktail, a mixer, on the rocks or neat, everyone’s different. The way you like to taste those things is going to be different to everybody else.”

This article is produced by Broadsheet in partnership with The Glen Grant