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Magic In The Maturation- Casks And The Role Of Fortified Wine By Derek King

Recently I was lucky enough to have Experience Irish Whiskey as part of the Irish launch of the beautiful 2025 Range Rover SV launch which saw guests enjoy a slice of modern luxury visiting ‘Range Rover House’ here in Dublin. The first time the concept has been executed in Ireland, it was without question the most beautiful activation I have ever been part of. Imagine this… 2 Michelin Star chef Jordan Bailey preparing your lunch, Champagne on a penthouse terrace, massages and whiskey tasting all while enjoying the view of this beautiful car!

Many of the guests I had the pleasure of meeting over the 10 days were very much non-whiskey drinkers for the majority. Interestingly, a vast number of the conversations started with “I don’t drink whiskey or I like the idea of enjoying a whiskey but not exactly sure how to start”. Most guests first felt the need to tell me what tipple of wine it is that they like.

This caused a slight change in the game plan and how I was going to present the three whiskeys in my arsenal over the course of the event. The whiskeys in question were Redbreast 12, Bushmills Causeway Sauternes and Two Stacks Polaris 1.2. Instead of dissecting the whiskeys and providing heavy detail from the off, I focused the main introduction around the finish or casks used for the seasoning of the expressions. In the case of these three whiskeys it was all sweet or fortified wine finishes.

The reactions to the details on the label and guiding a tasting this way was very interesting as now, all of a sudden, these new advocates were seeking some familiarity with their favourite wines. It made me consider the role of these sweet wines and what part they play in convincing wine drinkers that there is a whole other world out there waiting to be discovered!

The Redbreast of course synonymous with Sherry casks, Bushmills Causeway Collection using a huge variety of casks, but in this case it was French Sauternes and the Two Stacks Polaris enjoying a spin in a Cabernet France Ice wine barrel.

For me personally, I am really enjoying the variety in the ports, sherry and Madeira casks to mention a few right now and these particular styles might just be the perfect hook in the vein for anyone on the fence. The perception of these liquids is generally negative in the sense that we think of our granny when we think sherry or a dusty bottle of Harvey’s Bristol cream that only comes out at Christmas. 

Fortified wine is a type of wine that has had a distilled spirit, usually brandy, added to it. This process increases the alcohol content and can make the wine sweeter. The broad category of fortified wine includes not only port and sherry but also vermouth, madeira, and many more. What’s more, fortified wine is becoming more popular than ever, partly due to the curiosity pique when we see its description on our whiskey bottles as well as its use in trendy drinks such as Negronis and spritzes.


Maturation has always been the most fascinating part of the journey for me, so before we talk about fortified wine casks we can get the boring bit out of the way! Here’s a small insight into what exactly happens and why.

When a cask is first filled, a very exciting journey begins for the whiskey. Technically known as maturation, it can be broken down into three main parts: subtractive, additive, and interactive maturation.

Subtractive Maturation: This phase involves the whiskey losing some of its initial harshness. For instance some compounds, which can give off unpleasant notes like a smoking match or rubber, are absorbed by the charred inner surface of the barrels, filtered almost. These compounds also change into milder forms, allowing more pleasant flavours, such as esters to present themselves.

Additive Maturation: This is where the liquid starts to gain flavours and colour from the cask. Bourbon barrels, for example, impart hints of vanilla, coconut, and honey, while Sherry casks add rich notes like Christmas cake, fig and raisins.

Interactive Maturation: This involves complex reactions between the whiskey and the wood, including oxidation and evaporation. These interactions bring out new flavours that neither the whiskey nor the wood have on their own. Oxidation happens as the cask breathes, drawing in fresh air and expelling saturated air, which helps the whiskey develop a more balanced and fruity profile over time.

Evaporation: Known as the “angel’s share,” this process involves the gradual loss of alcohol and water from the cask, which helps eliminate undesirable elements and contributes to the whiskey’s complexity. The rate of evaporation, usually about 2% per year, depends on various factors like the type of warehouse and the cask’s position in it. 

A whiskey will develop a majority of its final character during maturation. Each cask offers a unique outcome, even when filled with the same batch of new make spirit (brand new whiskey) and stored in the same warehouse, due to the myriad factors at play, including micro-climates within the warehouse. Finally throw all these amazing fortified wine casks in the mix and the ante gets to different levels altogether.

Many distilleries also use a technique called “finishing”. This means the whiskey is aged in another type of cask (usually ex-bourbon) for most of its maturation, then transferred to a fortified wine cask for a short period before bottling. This is very common with these cask types.

Finishing in Wine Casks

Here’s a quick look at some of the popular wines and what to expect them to do to the taste of your whiskey. I have also included some of my tasting notes as well as whiskeys I suggest trying if this sounds like a bit of you!


Sherry is a diverse type of fortified wine from Andalusia, Spain. It ranges from dry and subtle (Fino) to rich and hearty (Oloroso), with other types like Amontillado, Moscatel, and Manzanilla in between. Sherry is fortified after fermentation, and some varieties are sweetened during production. It’s aged using the solera system, which involves transferring the wine between barrels. When used to finish or mature whiskey it delivers hints of nuttiness, dark fruits such as fig, prune and raisin. Earthiness can also sometimes be picked up. You can’t go wrong with a Bushmills Black Bush…a classic! I’ve also really enjoyed Skellig Small Batch PX Sherry Cask finish. If you really want to treat yourself The Palace Bar All Sherry Redbreast Single Cask is a phenomenal drop, and only available in the bar by the measure.


Port hails from the Duoro Valley in Portugal and comes in two main styles: Ruby and Tawny. Fortified with brandy before fermentation, port has a deep, rich flavour reminiscent of raspberries or cherries, making it a popular dessert wine often paired with chocolate or summer fruits. Port wood used for whiskey ageing is amazing, giving beautiful tastes of sweet red fruit, fragrant nutty notes and dark chocolate. Try West Cork Maritime Port Cask or Redbreast Tawny Port from their Iberian series- both great examples of the deep impact port finishing has on both Single Malt and Single Pot still whiskey.


Madeira is from the Madeira Islands off Portugal’s coast. It’s aged through a process of repeated heating and cooling, a method that originated from long sea voyages. Nowadays, it’s either artificially heated and cooled or aged in warm, sunny attics. We have seen a few brands thankfully venturing down the Madeira route and with this whiskey you can expect treacle toffee, sweet marzipan, orange peel and burnt sugar. Two examples of whiskeys I have enjoyed with the Madeira stamp were Micil Madeira Island Pot Still and Tyrconnell 10 Year Old Madeira Finish.


Marsala is a fortified white wine from Sicily, available in gold, amber, and ruby colours. Dry Marsala is great as an aperitif, while sweet Marsala is often used in cooking. All types of Marsala are valued for adding rich, nutty flavours to sauces and glazes. For me, when it comes to whiskey finishing, this is always about the tropical fruits, honey, citrus and stewed apricot. Boann Distillery’s The Whistler Mosaic Marsala is a superb whiskey as well as Drumshanbo Marsala Single Pot Still. Both great examples of Marsala loveliness!

These are four very common types of fortified wine, but there are many more to explore. Check with your local specialised whiskey shop. Celtic Whiskey, Dawson Street and James Fox, College Green lead the way in stocking all of these beautiful bottles.

In summary, the plethora of wine types we have access to has increased greatly but the influence of fortified wine casks continues to play a crucial role in creating new and exciting whiskeys that are inviting in the wave of new enthusiasts. Share them with the wine drinker in your life.. They are sure to thank you!


The Whiskey Journey derek king

Derek has worked in the traditional Irish bar scene for many years and holds a huge passion for Irish pub culture. His time has been served as a bartender, bar manager and proprietor of pubs and music venues. He has spent time working in many different countries including Australia and Canada broadening his understanding of how alcohol and bar culture differs from country to country.

Derek has gained broad whiskey knowledge through in-depth whiskey training events, whiskey tastings, masterclasses and multiple Midleton Academies. The majority of this exposure was gained during his role as Global Brand Ambassador for Powers Irish whiskey with Irish Distillers/Pernod Ricard

The love for whiskey and distilling became his career focus when he was part of the start up team at Slane Distillery (owned by Brown Forman/Jack Daniels). Derek was part of the commercial and operational management of the day to day running of the visitor centre, which was located on the grounds of the iconic Slane Castle. POWERS whiskey called next… Derek took the brand by the reigns travelling as their global spokesperson telling the most historic and rich brand histories of all the whiskey stories out there. Now through the establishment of Experience Irish Whiskey, Derek is ready to spread the good word of Irish whiskey with specialised whiskey tasting experiences throughout the four corners of Ireland.

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