When people talk about Australian whisky maturing faster than Scotch, they're usually talking about climate. But what does climate actually do to a cask, and why does it make such a difference?

There are two very distinct parts to making a whisky, the first part is producing the new make spirit itself. Where ingredients, fermentation and distillation all come into play.

The second part is maturation, with a very different set of levers to pull. Type of oak, the previous contents of the cask and the length of time the whisky spends ageing. All of these are important, but there is another factor that is just as significant: climate.

Whisky casks are not sealed containers. Oak is a natural material that expands and contracts as temperatures change. When the weather warms, the grain of the wood opens up and allows the spirit to penetrate deeper into the staves. When temperatures cool again, the wood contracts and the spirit is pushed back out into the barrel.

As this cycle repeats over and over, the cask gradually changes the whisky in several ways. It extracts flavour compounds from the oak, softens and integrates the spirit, and allows small amounts of oxygen to interact with the whisky over time. This slow exchange between wood, spirit and air is one of the most important parts of maturation.

The bigger the swings in temperature, the more active this process becomes.

This is one of the reasons Australian whisky often matures more quickly than whisky produced in cooler climates. Here in Kinglake, winters are genuinely cold, often dropping below freezing overnight, while summer temperatures can still climb well above 35°C. These seasonal changes encourage the casks to breathe more actively than they would in many traditional whisky regions.

The most visible sign that this work is taking place is something distillers refer to as the angel's share — the amount of whisky lost to evaporation each year.

In Scotland, annual losses of around 2–3% are common. In Australia, the figure can be significantly higher. In some of our smaller casks at Kinglake, annual evaporation can reach as much as 10%.

While nobody enjoys losing whisky, the angel's share is evidence that the cask is doing its job. A completely inactive barrel with no evaporation would not be changing the spirit very much at all.

Temperature, however, is only part of the story.

Humidity also plays an important role in maturation. In dry conditions, water tends to evaporate more readily from the cask. In more humid environments, alcohol can evaporate at a greater rate. The balance between temperature and humidity helps determine both how quickly a whisky matures and how its strength changes over time.

A finished whisky is the product of two distinct sets of factors. The first, during production, can largely be controlled by the distiller. The second, during maturation, is much more a product of the natural environment in which the distillery sits—and one of the reasons every place produces a different whisky. It's also one of the reasons Kinglake whisky could only ever be made in Kinglake.