Using oak barrels for ageing either spirits or wine is all about adding flavours from the wood and modulating existing flavours in the liquid. Using heat on the inside of the barrel will help to mellow the tanins naturally occurring in the wood and add spicy or vanilla notes that raw oak cannot impart. There are two options for applying this heat to the inside of the barrels – long gentle heat (known as toasting) or short fierce heat (known as charring). Getting the toasting or charring process just right is part of the art of a great cooper and whilst it can look effortless when done by an expert practitioner it requires a lot of experience to get it right every time.
Toasting can be done in an oven, but we use a naked flame to toast our barrels, although the flame will not come in contact with the wood. The idea is to gently heat the wood until it begins to darken in colour – the toast applied can be anything from light to heavy: the heavier the toast the more flavour the oak will transmit. Toasting is a much slower process than charring ( it takes around 10 minutes as opposed to 25 seconds for charring): this longer period allows the heat to penetrate deeper into the wood, whereas the char is a more superficial treatment.
Charring of the barrel means a naked flame must be applied and rather than just darkening the wood (as is done with toasting), the wood is actually burnt up to a depth of around 3mm (1/8th of an inch) and begins to charcoal. The char is too powerful to be used for wine, so is typically used just for distilled spirits. The charcoal acts as a sort of activated carbon filter which helps to remove sulphur compounds from the whisky (or other distilled spirit) helping to make it a smoother drink in a process also known as subtractive maturation. The char will also release spicy and sweet notes (as the sugars in the wood are caramelised) and give a characteristic smoky flavour and a darker colour to the whisky. We offer four levels of char – light, medium, heavy and extra heavy (also known as alligator).
Generally for our used port barrels we do not advise that any heat treatment is given to them, as much of the port wine flavours will be removed – we do have some clients who request some kind of heat treatment however.
If you would like some help in deciding exactly what is the best treatment for your barrels, please contact us to find our more.