Basically, wooden barrels.
Casks. What are casks? Traditionally, casks (barrels) are made of wood and are used to store and transport liquids from Medieval Times to the end of the Age of Sail. People definitely used casks to store water and/or wine in their homes for use and slowly, they realised that the casks impart a certain flavour to whatever is stored in them. In the case of wine/ales/beers, it amplified the flavour resulting in a better drink. Slowly, casking and cask ageing became a thing.
So, what is all this big fuss about cask ageing and the wood associated with it? To put simply, whisky in its purest form is just a white distillate derived from malted barley. This white spirit has some flavour but lacks a lot more ‘punch’ and maturity to become a fully aged whisky. For it to fully become whisky, it has to be stored in casks and aged, allowing it to fully developed and mature in the casks and thus become whisky. In the eyes of the law, Scottish whisky has to be aged a minimum of three years and not in casks exceeding 700L in volume. You can read more here about whisky regulations. (Soon! I promise!)
Now, if you think it is a good idea to start making cask and store your own white spirit to mature, I suggest you sit down and read more lest you desire wood sap for a drink.
This beast is where all them flavours come from.
Alright. Did I get your utmost attention? Great! As this post will be a very, very long one. Casks do not just come from any wood for cask ageing. Most, if not all come from the White Oak tree. See genus Quercus. Why? Because oak has consistently proven itself to impart its flavour to whatever is casked, and also history where wine is the staple and oak is one of the, if not the wood to use over centuries of human experimentation. The wood is porous enough to allow whatever is stored inside to seep into the grain, and allows some oxidation and evaporation to occur not to the extent of spoiling the stored liquid. The chemicals in the wood, such as the phenols and tannins impart their flavours into the liquids. Examples of these are the vanilla-y flavours and the silky (siap) mouth-feel.
Us humans have become incredibly creative in our search for better flavours. We also toast the oak casks to bring out certain flavours. From fresh oak to toasted and lastly, charred. If that is not enough, we also reuse barrels that have been filled with other liquids to get those flavours for whatever we want to age. Common examples would be Port, Sherry, Bourbon and Cognac. It is uncommon but you can even see Chardonnay casks and Calvados casks being used. It all depends on the flavours that one is interested in achieving. Below is the very rough breakdown of what you can expect for the different casks used to age your preferred choice of drink. I can only provide what is common as whisky casked in Calvados and Chardonnay barrels does not come easily anywhere.
Types of Casks
Sherry – Red fruits. e.g. Cranberries and Cherries and raisins.
Port – Dark fruits. e.g. Plums and Blackberries.
Cognac/Brandy – Grraaappppeeeeesssss. Simple sugars, fruits and flowers.
Bourbon – Vanilla, oak and wild flower honey.
French Oak – Oaky and Tannic. Silky mouthfeel with a bit of a bite. Think young red and white wine.
American Oak – Vanilla and alot less Tannic. Has a floral character.
Charred Sugar Maple – Jack Daniel’s. Maple syrup. Very sweet.
*Psst. I’ve included Wikipedia links for you book worms out there.
As mentioned, these are the common types of casks used to age your favourite distillate. I hope I am able to try the Mizunara aged ones because only Japan has it. Mizunara, is Japanese Oak which is used to age Umeshu (Japanese Plum Liquor). Fuji Gotemba, Mars Distillery and even Chivas seem to have Mizunara casked whisky for purchase, but only in Japan. Now, lets move on to the next part of the casks used to age whisky. This factors ranges from the time taken, humidity, temperature and even the location where the cask is placed in the warehouse. Some whiskies also undergo another period of cask ageing or ‘finishing’ to impart more flavours, or to ‘marry’ a whisky to smooth out and harmonize the blend, instead of just being blended and then bottled.
Surprise! Here comes India!
Humidity and Temperature
Ever heard of Amrut? It is an India-based distiller who makes single malts in hot, tropical and humid Bangalore. Average humidity is 65.2% and the temperature is 29.4 to 19.0 degree Celsius. Way more than the cold, balmy and dry Scottish lands. So what does this do the whisky? The high humidity lessens the amount of Angel’s share in the barrel and thus less whisky is lost every year. However, the temperature probably overcompensates for the humidity and 10% of the whisky in the barrel can be lost annually due to evaporation. Don’t get too ahead though as the higher temperatures allow the whisky to age a lot faster than the ones in Scotland. The temperature allows the casks’ pores to open up and gives more energy to the whisky to interact with the barrel and itself. So, an 3 to 5-year-old equivalent of an Amrut might feel as old as a 12-year-old from Scotland. Heck, I might even be wrong as I’ve yet to have the opportunity to try an Amrut, and the Amrut 8 years is a Limited Edition. Most of their range comprises of NAS which we covered here, and have been loved well and wide internationally.
The Kavalan Distillery Warehouse
A warehouse is a building with many shelves and racks. A barrel can be placed in the darkest, most isolated corner of the warehouse to the top shelf near the roof. What exactly does this do to the whisky? The higher you place the whisky, the higher the average temperature it is at that particular height. This increases the Angel’s Share but allows the whisky to mature faster as it concentrates the distillate. Put it in a dark corner of the warehouse? You have a whisky that is taking its time to age, mature and develop. You won’t really get to taste the effects of this as all whiskies are blended, unless it is a Single Barrel.
Be afraid. Very afraid.
Now you may be wondering. All whiskies come from a cask, but not all casks are made the same. Most use the de facto size of 200L as the U.S. law states that is the required size for bourbon to be aged in. But, as you can see above many sizes of barrels exists as the rest of the world carries on without such funny regulations. The Butt, Hogshead, Barrique and Quarter Cask are common. The Tun is something you probably hear from Game of Thrones or maybe even Monty Python. Basically it all boils down to this. The bigger the barrel, the longer it takes to impart its flavours. Vice versa for the smaller barrels. The smaller, the faster it takes. This is all related to the surface area in which the whisky is exposed to. So maybe sometimes you see a Laphroaig Quarter Cask lying around, don’t go “meh, what marketing gimmick is this? I’ll get the 10 instead.” Wrong! Try the Quarter Casks! But hey, both are amazing stuff for my peat head of a friend Jo, just not for me.
Multiple Casks Ageing
Now, this is where it gets interesting. Some whiskies only use a Sherry casks for their whiskies. However, many have opted to use multiple types of casks to age their whisky. By altering how long the whisky spends in certain casks, type and size, one can alter the flavour profile he or she wishes to achieve. An example would be a Glenlivet Master’s Distiller’s Reserve. This bad boy is aged in Ex Sherry, American Oak and lastly, plain Oak casks which they mentioned traditional. Maybe Glenlivet’s own? This is a prime example of ‘marrying’ a whisky or ageing the blended whisky.
The Solera System. Easier to understand than me writing it.
The last factor is quite limited. You have either the Master Blender or Blender to decide which whisky is blended and married together, or depend solely on a system. This system is called the Solera system originating from Spain. This system is used on Sherry, Port and Rum where the liquor is constantly mixed and blended with younger ones until you achieve one big consistent product that might even contain whisky from 50 years ago! Basically, the casks above which are younger are continuously taken to blend with an existing cask below. The lower you go, the older the product that is introduced to the blend, ending up with a Solera-based drink.
To sum it up, whisky ageing requires wooden casks, time and a few other factors as stated. Alot of work goes into one whisky and we shouldn’t just base one whisky off the age just because it’s too young. Be aware, and you can end up making decisions based on knowledge of cask ageing to get the flavour profiles that you want!
Alright! I should be about done! Took awhile and I hope I have briefly summed up about whisky and ageing it. I will continue to update this post as to my knowledge and I hope you’ve learned as much as I do!