FAQ - Cask Spirit Company


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Because it makes for a very unique and refined end product!  

At the Cask Spirit Company we transfer mature premium whisky into 4 gallon pin (18L) seasoned oak casks.  Up to 80% of the flavour components in dark spirits such as whisky, come from cask maturation, primarily from the wood.  By ‘finishing’ whisky with a conditioning liquid you can further refine the flavour (see below on the benefits of cask finishing).

We also love the tradition and theatre of serving spirits directly from the cask.  Plus casks reflect beautiful craftsmanship and make for stunning features in a range of venue

During the first few years of barrel maturation, the new spirit becomes softer and rounder and the new spirit’s less desirable smells and flavours vanish. The barrel breathes, allowing the harsh volatile alcohols to escape from the cask.  These are replaced with air to allow the spirit to oxidise. Oxidation produces many new compounds that lead to a complex aroma spectrum in the spirit. 

By transferring matured spirits to small oak casks, we can further refine the characteristics of the spirit and introduce a conditioning liquid such as port or sherry (see below on ‘cask finishing’). 

If you’re interested in learning more about the science of maturing read more here

Oak is flexible and highly durable and an oak cask will last for decades. Distillers prefer clean wood with little resin (which can add an undesirable flavour).  Also, without resin, the wood is more porous enabling the casks to “breathe.” 

American white oak has a low tannin content and produces vanilla and coconut aromas making for a sweeter profile.  Oaks, mainly from France and Spain, are more porous, allowing for more maturation. This wood is darker with a complex spectrum of aromas, including leather and nut flavours. The high tannins in European oak provide a more robust flavour.

More exotic non-oak timber can also be used for spirit-ageing, such as cherry or hickory.

Our oak casks have previously had liquids in them so that any astringent flavours of virgin oak are removed. Each time a cask is filled with a spirit the liquid will take in the flavours and properties from the wood during the ageing process. The wood will absorb some of the liquid in return. This is why a first-fill cask will give out a lot more flavour and colour to a whisky for example than second or third-fill ones (see below for why American Bourbon only uses new oak).
By working with repurposed wood as well as conditioning your cask, we ensure that the wood is at its optimum prior to filling and finishing your chosen spirit.

Toasting and charring are both methods used to prepare barrels for ageing spirits, but they involve different levels of heat and duration. Toasting consists in heating the inside of the barrel with a low flame to lightly toast the wood, breaking down some of the hemicelluloses and creating flavours like caramel, vanilla, and coconut and a complete spectrum of chemical reactions to produce flavour molecules for the spirit to absorb and react with. Charring, on the other hand, involves exposing the inside of the barrel to a high flame, which chars the wood and creates a layer of charcoal. This can add smoky, spicy flavours to the spirit. As well as opens up the surface of the wood to increase surface area, which is essential for the interaction with the barrel. We toast and char all of our barrels to ensure full flavour development.
The charring creates a series of chemical reactions that release vanillin, caramel, and other compounds that give whisky one of its characteristic flavours. The char also opens up the wood’s pores, allowing the whisky to interact with the wood and extract more flavour compounds more efficiently. The level of charring can vary depending on the desired flavour profile. For example, a lighter char will produce a more delicate whisky, while a heavier char will produce a more robust whisky with smoky notes. Here are some of the specific reasons why coopers char barrels for making whisky: Vanillin: Vanillin is a compound that is naturally found in oak wood. The vanillin is released when the barrel is charred, imparting a vanilla flavour to the whisky. Caramel: Caramel is another compound that is released during the charring process. Caramel gives the whisky a sweet, mellow flavour. Other compounds: The charring process releases other compounds, such as esters, lactones, and phenols. These compounds contribute to the complexity and richness of the whisky’s flavour. Opens up the pores of the wood: The charring process also opens up the pores, allowing the whisky to interact more easily with the wood and extract more flavour.
Barrels are toasted (heated) in addition to charring with a flame. The level of toasting will differ depending on the required flavour style. For example, bourbon is typically aged in heavily charred barrels, while Scotch whisky is generally aged in a lightly charred cask but with more toasting.
Toasting is essential for the following:
  • To mellow the tannins in the wood. Tannins are naturally occurring compounds in oak wood that can give the whisky a harsh, astringent flavour. Toasting the wood helps break down the tannins, resulting in a smoother, mellow whisky.
  • To create a more complex flavour profile. Toasting the wood releases various other compounds, such as vanillin, caramel, and esters. These compounds add depth and complexity to the whisky’s flavour.
  • To open up the pores of the wood. The pores of oak wood are tiny, making it difficult for the whisky to interact with the wood. Toasting opens up the pores, so the spirit can extract flavour more easily from the wood.
  • To create a consistent flavour profile. The charring process is relatively inconsistent, so toasting the barrels in addition to charring can help to create a more consistent flavour profile from batch to batch.

We source our casks from two cooperages. 

For our premium bespoke casks we work with an in-house journeyman cooper based at Theakstons Brewery in Yorkshire.  A coopering apprenticeship takes four years to complete and ends with a ‘trussing in’ ceremony which is the initiation into the Federation of Coopers.

We also work with the D’Barril cooperage, located just south of Porto in Portugal.  They have a 50 year history of producing casks from European oak. 


A cask is a generic term for a wooden vessel created for maturing spirits. They come in various sizes and each size has a specific name.   A barrel is a type of cask that is 50–53 gallons or 180–200 litres.

Other sizes of cask are named the following:

Blood-tub 30 to 40 Lt

Octave 50Lt

Quarter casks 125Lt

American Standard Barrel 200Lt

Hogshead 230-250 Lt

Port Pipe 350Lt

Butt 500Lt

Puncheon 500 – 700 Lt

At the Cask Spirit Company we specialise in finishing spirits in 4 gallon pin casks (18L).  However, we can work with our cooper to break down speciality larger sized casks into the size you require. 

Smaller casks have a greater liquid to surface ratio compared to larger casks, allowing the spirit to have more contact with the surface of the wood. For example, a 20Lt cask matures four times as fast as a 200Lt barrel.

‘Finishing’ a spirit in a cask previously containing a conditioning liquid adds a further nuance and complexity to the spirit than the impact of the wood alone.

In the same way a spirit will absorb some of the flavours of the oak wood, a cask that previously contained port, for example, will naturally take on some of the elements of the port thereby adding a fruity profile to the spirit in the cask.

When a cask is conditioned with a liquid, chemical changes take place in the wood which then carry specific flavour characteristics to the spirit in the cask. These are more nuanced and interesting than both the finishing liquid and the spirit. For example a cask conditioned with Pedro Ximenez Sherry, does not make a whisky taste of Pedro Ximenez Sherry, but a much more complex flavour that is derived from the chemical reaction within the wood.

At the Cask Spirit Company you have the option of ‘finishing’ your chosen spirit with oak that has previously contained one of three conditioning liquids – Pedro Ximenez Sherry, Vintage Ruby Port or Classic Madeira Wine.

Casks seasoned with Oloroso are the most common type of sherry barrel used in scotch whisky. Oloroso imparts deep dried fruit notes like figs, dates, spice, and nuttiness.

Oloroso casks are the most versatile and great for finishing all whisky styles, rum and cognac.

Pedro Ximenez (PX) is a sweeter Sherry than Oloroso. Casks seasoned in PX are fantastic for finishing robust, heavily peated Islay whiskies and oaky Bourbon and Ryes.
The additional sweetness rounds off the phenolic notes of peated whiskey, producing a beautifully balanced spirit. Also, PX is the best choice if you prefer rum on the sweeter side.

Ruby Port leaves a residue of red anthocyanin pigment ingrained in the barrel’s wood that is transferred to the spirit during finishing. In addition to a red hue, Port will deliver a flavour of forest berries with dark chocolate and a fragrant character.  Port compliments elegant spirits such as Cognac and Speyside malts.

Madeira is heated while ageing, unlike sherry, resulting in caramel, dried fruits, and baking spices notes, with a vanilla aroma. Compared with sherry and port, finishing spirits in Madeira casks are less typical, but it’s becoming increasingly trendy. Spirits matured in Madeira casks take up the subtle but sophisticated aromas of spice and fruit of the Madeira Wine.  A natural finishing choice for smooth, light floral spirits such as Cognac and Lowland malt whisky.   

Although finishing whisky at home is an economical way of acquiring excellent whisky that would otherwise be expensive if purchased pre-finished, it should not be considered an investment vehicle.  Drink, enjoy and share your whisky instead.

In the last 12 months, there has been a significant increase in the advertising and promotion of whisky cask investment schemes across all media channels. If you are considering investing in a whisky cask, we urge you to proceed with caution. Please read the following articles for further information.



As every cask is unique, pricing will vary based on your choices around cask wood, whisky and conditioning liquid.  A typical cost is around £2.5K (the lowest cost options available start from  £1k and exclusive whiskies in the region of £20k).  Due to our relationships and reputation we have access to the best market prices and we will provide a detailed quotation to you ahead of order and invoice.


We have relationships with many quality distillers and brokers and occasionally we buy fine spirits from auction.  

This gives us access to an unparalleled range of fine and rare cask-strength whiskies across the five Scottish regions – Campbeltown, Highland, Islay, Lowland and Speyside.  All of the whiskies we source are pre-matured, aged from as little as 3 years to as many as 20 years

A cask-strength spirit is a spirit that is at the same alcohol by volume (ABV) as it was when it was removed from the maturation barrel. This means it has not been diluted with water and typically has an ABV of 55 and 65%. Cask-strength spirits are often more intense and flavourful than their diluted counterparts, as the higher alcohol content preserves more of the natural flavours of the spirit.  Water or ice can be added according to preference. 

At the Cask Spirit Company, we only fill our casks with spirits ranging between 55-60% ABV. The higher alcohol content of cask-strength whisky allows for more interaction with the barrel’s wood. This can impart additional flavours and aromas to the whisky. Also, when the spirit is poured from the cask, you can control the strength of the whisky by adding water or ice to taste. This can create a more personalised drinking experience.

It is important to note that spirit evaporation will naturally occur as part of the ageing process in the cask.  Typically more alcohol than water will evaporate, but if stored in a warm, dry room, more water will evaporate than alcohol, and the % ABV gets stronger. 

The amount of distilled spirit lost to evaporation from the cask into the air as the spirit ages is called the Angels Share.  The amount of Angels Share lost varies widely depending on cask size, time, environmental conditions and location within a room or building.

Note that evaporation in smaller casks is quicker due to the greater surface area to volume ratio.  It will be further exaggerated if not stored in a cool room.

An interesting way to illustrate the factors impacting evaporation, is to look at distillers around the world.  One year maturing in a warm and humid climate like Kentucky USA is completely different to one year in a milder climate like the Isle of Islay.  Scottish distillers are allowed to write off 2% of their production volume each year to the Angel’s Share. When it comes to Kentucky Bourbon or Tennessee whiskey their Angel’s Share may average closer to 4% and could be as high as 10% in the first year. 

Yes, your spirit will improve over time. The spirits we work with are already fully matured prior to being transfered to their finishing casks. The conditioning liquid embedded in the wood of the new smaller cask now hosting your spirit will continue to influence and nuance the flavour. Although the rate of change diminishes over time, there will be subtle improvements the longer you leave your spirit in the cask.

The rate of change is individual to each cask, with the size of the cask being one of the most significant factors. The smaller the cask, the greater the rate of change. Temperature and humidity will also influence changes.

American law states that Bourbon must be aged in new casks. New wood has a lot more influence on the spirit than wood in a second filled cask where the tannins and other flavour compounds have been depleted. Fortunately, Bourbon needs a significantly shorter maturation period, typically between 3 months and 3 years so the use of new wood can be tolerated. This is advantageous for the Scotch whisky industry as they often use surplus bourbon barrels from the USA. This is important as Scotch whisky must be matured for a minimum of 3 years, and fine whisky typically ten or older and new wood would not be suitable.

Order Process

We will work with proven combinations of cask, finishing liquid and spirit. We hope that the information provided on the ‘Finishing’ page of the website gives you an initial level of detail. 

When you create your bespoke luxury cask Matt Servini, Master Distiller and cask expert, will work with through the options with you and will provide advice on your choice. 

A 4 gallon, 18litre, pin cask produces 24 x 70cl bottles or 336 x 50ml measures.

However, do read the section above explaining the natural evaporation process known as the ‘Angels Share’.

And remember that our spirits have a higher ABV (Alcohol by Volume) than standard bottled spirits.

Absolutely. We can provide a standard template for you to complete or if you have specific wording or visuals in a pdf you want us to etch (providing it fits!), you can attach and send it to us.

Each cask comes with its own spirit certificate detailing:

  • Maturing cask wood origin
  • Distillery
  • Region & style of spirit
  • % ABV
  • Age prior to finishing
  • Date of finishing cask fill
  • Wood/ Origin of finishing cask
  • Toasting
  • Final conditioning liquid (if chosen)

Cask Care Instructions accompany the certificate, including recommendations for storage, guidance on decanting and the expectation of flavour development over time.

Depending on the choice of wood and spirit, it can take between 2 and 8 weeks to create and ship your cask.  

For our bespoke casks, we arrange custom packaging and shipment to ensure optimum protection.


Whilst we take significant pride in the quality of our casks, there is always the occasional risk of a potential leak with a natural product. We are confident that our packaging will fully protect the cask but if you have any problems do let us know.


If the care instructions are followed, providing there is sufficient liquid in the cask, it should remain leak-free for decades. 

On occasion, if a cask has dried out or had a knock, a pin-hole leak may develop. We provide a bar of natural beeswax with every order to treat affected areas and seal leaks.  

The ideal environment would be cool and damp, however, if cared for appropriately, a cask can be stored in any typical home where there are no extreme fluctuations in temperature. The optimum temperature range is 5°C to 15°C. The maximum and minimum range we would recommend is 1°C to 25°C. The cask will benefit from occasional ‘turning’ – moving or gently ‘swooshing’ the spirit around in the cask, so liquid touches all parts of the interior wood. Ideally this would be done once a week or a minimum of once a month. It is advisable that when there is less than 20% liquid remaining in the cask, it is decanted as there’s a risk of the top of the cask drying out. If you want to reuse your cask after decanting, we recommend filling your cask with slightly salted water ahead of refilling (see below on refilling).

The ideal environment would be cool and damp, however, if cared for appropriately, a cask could be stored in any typical dwelling where there are no extreme fluctuations of temperature (specifically heat).

Yes, providing it hasn’t dried out (see note on Caring for My Cask above). 

If you plan to refill your cask at a point in the future after having emptied it, we advise you to fill the cask with non-chlorinated water and 5% salt to keep the cask moist. At the point you are ready to refill, remember to wash out the salt water!

If your cask is in a good condition, we will consider buying it back provided it’s got a small amount of liquid left in the cask to prevent it drying out.

No, a rejuvenated cask has generally been used three times and the flavour and colour of the wood has become exhausted. At this point casks can be returned to the coopers to be re-charred and rejuvenated, giving them a whole new lease of life.

Wood is one of the most sustainable and environmentally friendly construction materials available. Not only does it absorb carbon dioxide while growing, it is also extremely adaptable and recyclable.

Our cooperage partners only work with repurposed wood from European or North American oak from natural indigenous forests. 

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