Barrel and bottle ageing chart
Firstly a few reminders from Barrel Ageing Part 1:
Ageing a badly made cocktail is not going to make it better! Use reasonable ingredients and make it with the outcome in mind - if you are aiming to add a lot of sweet flavours from a small bourbon barrel for example, it might pay to make the drink a little drier.
Don't age anything that will go off. Goes without saying really, but old dairy or rotting fruit juices aren't going to do you any favours!
If you're buying new barrels, make sure they aren't lined with lacquer or treated with (potentially toxic) wood preservatives. They need to be food-safe quality.
The smaller the barrel, the faster and more intense the effect will be. If you want an aged cocktail for a competition next week, or have high turnover in a busy bar, you might like to use new 5-litre barrels. Small barrels mean more contact between the liquid and the surface area of the wood.
All vessel types below will probably soften and mellow a cocktail, except where oxidation might lead to acidification - if the alcohol beverage volume (ABV) of the drink isn't high enough, wines and vermouths can oxidise to acetic acid in the same way an open bottle of wine goes sour in a few days. In this case, an airtight bottle might be a good bet.
The chart below lists 10 barrel types, the flavour profiles they would intensify and my recommendations for the cocktails you could try aging in them. It also includes notes on bottle ageing (as championed by Tony Conigliaro around ten years ago) which allows the ingredients to mellow, mature and soften, much like ageing a fine wine. For more ideas around bottle serves, click here.
The darker the colour, the more pronounced the effect:

Paul Mathew is a bar owner, drinks consultant and writer. He is based in Cambodia, owns a bar in London, and regularly travels in-between looking at bartending styles and trends.