The cask, the wood, The Angel’s Share,… If a part of the whisky magic is happening in the still room, another part is happening in the cask. There are huge debates about the percentage of the flavour that is actually brought by the cask itself but for sure it has its huge importance and it is not just only a stage to avoid putting an Ages Statement on the bottle and play a marketing trick advertising unusual, original, experimental maturations and finishes (well… Sometimes it is to be fair!). The industry consensus is to say that 65% of the flavour is coming from the cask. However, one thing is absolutely sure, the cask is responsible for 100% of the colour!
Whisky will only mature in the cask, maturation is a combination of evaporation (the Angels’ Share), abortion, wood extraction and chemical reaction.
To appreciate what the cask is bringing in terms of flavour, having a chance to nose (and taste for the most courageous) new make spirit is very useful. New make spirit is not neutral by any means: wheat spirit is surprisingly floral, malt spirit very grainy for example. If you were to choose to drink new make spirit (it would be compared to some kind of eau de vie), the nose is definitely more attractive on the grain spirit. This is why, generally speaking, malt whisky needs more maturation than grain whisky, grain whisky is reaching its peak in a quicker way.
Whisky has to spend 3 years and one day in a cask according to Scotch Whisky Regulations and the size of the cask cannot exceed 700L. Why? A question of ratio surface to volume. Let’s assume cylindrical casks, the following graph is showing the surface to volume ratio depending on the radius of the base:
A 250L cask with a base of 35 cm radius, assuming it is cylindrical, the height would be 65cm, make rough sense. That would make a ratio of 0.09. Here is the formula:
To reach the same ratio with a 700L cask, it would need to have a 24cm radius but a height of 3.87m! Highly unpractical! The base of a 700L cask will obviously be larger than a 250L cask, else it would be very difficult to build, expensive, and difficult to manipulate! So assuming more normal dimension, a 45cm radius, a 700L cask (cylindrical) would be 1.10m high and the ratio would be 28% lower than a 250L cask. Small casks are obviously better for surface to volume ratio, the example on a 50L cask is obvious: with a radius of 20cm, the ratio would be 71% higher than the 250L cask. Why not maturing the whole production in 50L casks? Unfortunately, 5 casks of 50L are much more expensive than a 250L cask, it also takes much more space as far as storage is concerned. The choice of the size of the cask is a compromise between the surface to volume ratio (the greater the better, it has a direct impact on the speed of the maturation), the cost, and the warehousing space available. This was for the scientific part, cask are not cylindrical anyway.
What about the 25,000L Solera process of Glenfiddich if 700L is the maximum allowed? Good question! The whisky is not actually maturing in the sense of the regulations, maturation has stopped, and the Solera is used for marrying the different casks (Sherry, Bourbon and New Oak) and mixing to old batches as it is never fully emptied (it is difficult to demonstrate in practice, but traces of the very first liquid filled in the tun would still be present after 50 batches). So, the whisky stops maturing, a 10 years old Scotch whisky that would be put in a Solera for 2 years would stay a 10 years old (the are usually resting in the Solera for 3 to 9 months). Also, a Solera vat is not intending to bring flavour itself, and marrying vats are usually in pinewood, more neutral in term of flavours and here also, as far as Regulation is concerned, a pinewood cask would not be good for maturation: oak only!
To go back on the maths, if a 25,000L vat is half emptied, how much of the original content is left after 10 batches?
It is going fast! It is like the Zeno’s Paradoxe of Achilles and the Tortoise. Achilles will never catch the tortoise, the vat will never be empty. But after 50 times, only a tiny wee dram will be in!
So it is not technically untrue to say there will ever be some of the original spirit in the vat, however, it becomes far-fetched (below a litre!) after 15 batches.
Anyway, back to the wood, quite a lot of the distilleries are having a cask stage in their visit one way or another: nosing, visualizing the angel share, the tipping, the filling, the warehouse,… So the Single Malt Tour could not ignore the cooperage industry and a Special Issue became obviously necessary. Indeed, driving from Aberlour to Dufftown, whether driving through Craigallachie or the cheeky shortcut through the Bluehill quarry, one cannot miss Speyside Cooperage.
It feels like the Egyptian pyramids, a mountain of casks piled up. Ancient Egyptians were drinking beer by the way, quite a lot! So these pyramids of cask can be seen as quite symbolic! But SpeySide Cooperage is much more contemporary, it was established in 1947 and is part of a French company called Tonnellerie François Frères since 2008. The business of the French company is leaning towards French Burgundy wine but has an international presence.
Speyside Cooperage has a visitor centre, a shop and a coffee shop. The basic visit is such a bargain, £4, it would be criminal not to stop and people are really nice… And very competent! The great David McKenzie is the world record holder, he built a 190L barrel in 3 minutes and 3 seconds.
The visit is probably slightly nicer in summer, December was a bad timing as it was snowing. Indeed, there is a nice set up for picnics, obviously with a barrel and wood theme. Very pretty for sure.
The visit is starting by a short movie to introduce the company and explain the process of building the cask and the process of the sourcing of the wood. An older version of the film can be found on Youtube.
The white oak is sourced in the US, mainly in Missouri, Kentucky and Tennessee. It has to be oak as far as the regulation is concerned: it is as a matter of fact a very suitable wood as it needs to be watertight but also the content needs to breath. Also, the flavour of the wood is an important component. Oak is therefore the go to wood, which can be proven challenging as far as sustainability is concerned as an oak can take 150 years to grow: ‘Acorn to Cask’ is a long process! There are different grades of oak and inside the same oak there are different grades of grain as the wood is not homogenous by any meas. Interesting to see the way the trunk is cut, initially quartered.
The wood needs to be aged and dried (at least 18 months to be fit for purpose) before it is shipped in Scotland ad transformed into casks. The staves are cut in the concave and convex required shapes before the assembly can start. When the initial first assembly is made, cask is a it awkward looking, like cylindrical or conical, therefore, it is steamed to soften the wood to bend it more easily. Then there is the toasting and charring process to bring some more flavour (caramel and vanilla notably) and helps the filtration of impurities in the whisky, open the grain of the cask. The process of building the cask is fully manual and there is no glue or whatsoever (even on the head, despite also being 3 or 4 piece of woods, only wooden dowels are used): wood, metal hoops and straw on the head jointure. The cooper will only use his hands and mainly 2 tools: his mallet and a hoop driver. There is obviously some machinery involved for example for quality control and wood cutting but most of the tools are old fashioned tools and they haven’t changed since years, a very traditional craft! The bunk hole is made right at the end.
A significant share of the business of SpeySide Cooperage is repairing and rejuvenating casks. Actually, new oak casks are quite marginally used. So distilleries are sending casks for repair, or rejuvenating. To extend the lifespan, a cask ca be de-charred to expose some fresh wood, and then re-charred.
They also have their own label, Acorn to Cask 10 Years Old Speyside Single Malt. Where does it come from is a well kept secret, a bit like the Copper Dog Single Malt of the Craigallachie Hotel… However, a hint on the movie could potentially suggest Glen Grant but this is pure speculation.
The movie is quite sensorial as heating lamp is flashing when the charring process is described, nice touch! A so called 4D experience.
Then the visit is very much self-contained, a guide is taking visitors into the gallery where coopers are working. Despite the noise and the apparent mess it is actually very organised!
There is an apprentice scheme and coopers are transmitting their knowledge. They are self-employed, meaning they are basically paid per cask. No wonder why they try to make them fast! But there is no compromise about quality and every single cask is tested when completed and sent back to the cooper if there is an issue. It is tested mainly by injecting pressurised air and water into the cask… No leak please! Else… Tray again!
The gallery is full of memorabilia, tools, instructions and is a well organised little museum. For £4 this is a bargain. There is a VIP tour also, where visitors can come down and spend a bit of time with a cooper.
Visitors can get their hand on a tiny little cask. Easy peays? Well… Have a try! Let’s put it this way, it took a bit longer than the world record to perform the assembly! For those failing the attempt, don’t forget, “it’s a poor craftsman that blames his tools”.
To conclude, a visit that is well worth as very few distilleries have their own cooperage, and when they do, apart from VIP tours, usually the visitor is not taken thorough the cooperage but at best just around a barrel with dismounted staves and a couple of tools.
This is therefore a useful visit for those interested in the grain to glass process and not only about distilleries.
SpeySide Cooperage: http://speysidecooperage.co.uk/
Tonnellerie François Frères: https://www.francoisfreres.com/fr/
Speyside Cooperage World Record: https://vimeo.com/215507436
Visitor Centre Movie – Old Version: https://www.youtube.com/watch?v=8NvCQfRoAmU
Beer in Ancient Egypt: https://www.ancient.eu/article/1033/beer-in-ancient-egypt/
How does a Solera mature whisky?: https://scotchwhisky.com/magazine/ask-the-professor/11668/how-does-a-solera-mature-whisky/
Zeno’s Paradoxes: https://en.wikipedia.org/wiki/Zeno%27s_paradoxes
Glenfiddich – A heritage on innovation: our Solera vat: https://www.glenfiddich.com/uk/explore/expert-blog/2013/a-heritage-of-innovation-our-solera-vat/
The art of barrel making: http://www.traveling-in-norway.com/no/barrel-pictures.php
Cooperage – The Art of oak ageing: http://www.decanter.com/features/cooperage-the-art-of-oak-ageing-245755/
Barrel making: http://bakerblockmuseum.org/heritage/cooper/barrelmaking.htm