Our motto at HYDE Whiskey is “It’s all about the wood”

It is well recognised that up to 80% of any final whiskey taste is as a direct result of the interaction between the maturing ‘new make’ whiskey and the wooden cask in which it is aged.

As such, Cask Wood Management is our primary area of focus and expertise.

The whiskey maturation process is influenced by many subtleties such as local climate and how the oak casks are stored and managed as the whiskey matures to final perfection.

At HYDE we carefully select only the very finest Irish whiskey, made by only the very best Irish distilleries, and we then finish this whiskey in vintage oak casks that we source from around the world.

We primarily finish our whiskey in Bourbon, Sherry, Rum and Burgundy casks. But we are also experimenting on aging HYDE whiskey in Port, Madeira, Cognac and even Beer casks.

  • Sherry Cask Finish 250L toasted Oloroso Sherry Hogshead casks from Jerez de la Frontera, Cádiz, in Southern Spain.
  • Dark Rum Cask Finish 200L Char flamed dark Rum casks from the Island of  Barbados in the Caribbean.
  • BURGUNDY CASK Finish 228L Ex-Burgundy vintage red wine casks (Pinot Noir) from the Cote d’Or vineyards near Dijon,  France.
  • Bourbon Barrels 200L ex-bourbon barrels from Kentucky in the United States of America.

We flame a specific char level to each vintage oak cask type before filling in order to create award winning Irish whiskey which is rich in character and truly unique in taste.

The time and effort that we put in to sourcing our vintage oak casks from around the world is what allows us to take a great Irish whiskey and make it taste event better. This is why we have won just so many internationally recognised awards for our HYDE whiskey.

We also source new make whiskey, made to our own very strict specifications, from two great Irish distilleries. This ‘new make’ whiskey spirit is then laid down for many years to  age and mature in our own casks at our Bonded warehouse in Little Island, County Cork.


The majority of Oloroso Sherry and Rum Casks are made from imported American Oak (Quercus Alba). As a member of the Beech Family, of the genus Quercus, Oak has large radial grains of high density that grow straighter than the majority of other hardwoods, making it perfect for tight cooperage.

More importantly, however, are the natural chemical compounds found inside oak which impart flavours, sugars, aromas and body to the maturing whiskey.

US law decrees that every American Bourbon barrel must be manufactured from Quercus Alba – American White Oak and that each cask can only be used once for the bourbon maturation process. All our whiskey is originally aged in American Bourbon casks, before being finished in either a Sherry or a Rum cask.

Oak is a natural, organic material and behaves as such, interacting with the whiskey as it ages and matures.


An average of four barrels can be made from one good oak tree. All our casks are quarter sawn which offers increased structural integrity as well as less expansion and contraction of the plank width.

The trunks are quartered (quarter sawn) to obtain lengths for the barrel staves by means of splitting and not cutting. This avoids destroying wood veins, important in whiskey maturation. Splitting is done while the wood is still green, as it is less susceptible to snapping.

The staves are then planed into rough shapes (called murrain) and stacked outside for between three and five years, after which they develop a silvery-grey finish, darkened as a reaction to the seepage of heavy tannins from the wood.

Only after this period, and once each stave has been inspected, are they planed to the exact specifications of the cooper and shipped out for cask assembly.

It is this attention to detail that makes HYDE Single Malt Whiskey so unique and rich in flavour, creating what we hope is not only a fine whiskey, but the very best premium whiskey Ireland has to offer.


The size of the cask has a big effect on the overall maturation of the whiskey and the final flavour profile.

The relative surface area of the wood to the spirit will influence the speed at which flavour compounds are extracted from the carefully coopered staves and absorbed into the whiskey itself. The smaller the cask, the greater the surface area touching the whiskey contained within.

With a smaller wood to liquid ratio, ‘Hogsheads’ react better to the temperate County Cork climate. This is why we use smaller 250 litre Oloroso sherry casks and 200 litre rum casks.

At 240 litres, ‘hogsheads’ are twice the size of a Barrel, half the size of a Butt and quarter of a Tun. These ‘hogshead’ Sherry casks are far more expensive, but worth every cent for their richer character and the natural colour they impart as we mature HYDE Single Malt Whiskey.


We flame-char our Bourbon and Rum casks at at least 250° Celsius (482°F) for between 15 and 45 seconds.

From light charring to a thick ‘alligator skin’ layer of charcoal, this process opens the wood grain making it more porous for the whiskey to enter.

Three reasons why casks are charred at 250°C are:

1) To generate a layer of active carbon which removes undesirable flavour substances in the new make whiskey.

2) To effect the release and dissolution of flavour compounds such as vanillin during the maturation process.

3) To yield colour and phenolic substances which result in new flavour compounds by oxidative interactive reactions with the whiskey.

In basic terms, charring helps to open up micro-channels in the wood allowing the whiskey to absorb deep into the oak, further extracting aromatic aldehydes, increasing the release of vanillins and absorbing undesirable flavours in the process.

The heat from the flame converts the inert wood compounds into strong, rich flavourful elements that are transferred into the whiskey during the long aging process. This layer of charred carbon charcoal also extracts unwanted, nasty flavours and compounds from the original new make whiskey.

By converting the top layer of oak into carbon charcoal, some of the wood sugars (hemicellulose) are converted into caramel notes while also acting like an active carbon filter in a water bottle or filter jug, removing unpleasant sulphur flavour compounds in the whiskey.

While charring is an exciting process to witness in any cooperage, as always, there is further devil in the detail. The temperature level reached and the length of time that the cask is subjected to the flame all makes a bit impact on the final flavour effect of the cask on the whiskey.

There are generally four ‘char levels’ simply graded from 1 to 4 with the lower number representing shorter exposure to heat and a softer char level.

  •      NO. 1 CHAR: 15 seconds – Lightly toasted
  •      NO. 2 CHAR: 30 seconds
  •      NO. 3 CHAR: 45 seconds
  •      NO. 4 CHAR: 55 seconds – Known as ‘alligator char’ due to its open textured skin.

The lighter char preserves more of the natural oak aroma and flavour (think a little spicy, a little earthy, with a touch of cedar). The heavier char provides more colour and caramelisation. Tannins will vary between these two types of barrels. The heavier char can also provide more of a sweet smoke note, which is often desired.


We toast our Oloroso ‘Hogshead’ sherry casks at between 100°C and 200°C (212°F and 392°F) for 15 to 35 minutes.

This slower and gentler toasting effect is classified from light to heavy toast.


– c/o







Our 250 litre vintage ‘Hogshead’ Oloroso sherry casks are sourced directly from a Bodega in the province of Cádiz in the Andalucía region of Southwest Spain.

HYDE Sherry finished whiskey is matured in these traditional Spanish ex-Oloroso Sherry casks.

The majority of the whiskey industry use American Ex-Bourbon barrels for their full maturation process. HYDE, however, starts with bourbon cask and finishes with a Sherry cask.

Sherry is a Spanish white wine which has been fortified by the addition of spirit distilled from grapes. This combination of the two is subsequently aged in oak casks.

The high acidity and lower alcohol content of Sherry have a very unique effect on the cask wood, providing more water-soluble flavours from the staves. These two factors combine to make whiskey matured in a Sherry barrel a unique and unmistakable experience. In fact, no cask has a more dramatic effect on a maturing whiskey.

The Spanish Oloroso sherry cask gives colour, spice and dried fruit with a robust dark and nutty character, whereas US Bourbon oak casks give a lighter, sweeter, vanilla and butterscotch flavour.




Our 200 litre vintage dark Rum casks are sourced directly from the island of Barbados in the Caribbean.

We spend an an exceptional amount of time hand-selecting, maturing and supervising the development of our whiskey to achieve a careful balance between the maturing whiskey and the influence of the wood in which it is aging.

At HYDE we know from experience that the maturation process is more important than the actual distillation process itself.

We know that the final taste of our whiskey is a direct result of the wood and the environment in which it was aged. It is all about the wood!

Each and every cask we use to age HYDE Irish Whiskey is hand-picked, directly from source and we only select the very best vintage oak casks for our maturation process.



Our Burgundy red wine casks come from the Burgundy region of France from the Côte d’Or vineyards near Dijon, France.

Burgundy red wine is made from Pinot noir grapes which ferment the whole grape that is crushed before fermentation.

Hyde No.5 Burgundy finish is matured in US Ex-Bourbon casks for 6 years and then is finished in French Ex-Burgundy red wine oak casks (228 litres) from the Côte d’Or for a further 9 months.

This leads to a wonderfully ruby-red colour in the HYDE No.5 Single Grain.



Cask management is the process of sampling casks as they mature, deciding when to bottle the whiskey and weather to leave it to mature a little further.

Learning to allow a cask to reach its full potential, undeterred by demand or necessity, is the hardest skill of all and one in which we take great pride.

The longer a whiskey is in cask, the more sampling is required in order to get the bottling time just right and to ensure a complex, subtle and balanced whiskey.

We regularly draw samples from our casks to determine when the whiskey has reached the prefect level of maturity and balance.

As well as the welcome flavour notes, the original new-make spirit can often have sharp unwanted flavour notes, described as harsh and metallic.

A good quality cask will remove these compounds over time as the whiskey breaths in and out of the wood and the charcoal layer inside.


The warm Atlantic Gulf stream provides County Cork with the perfect temperate, oceanic microclimate for maturing Irish Whiskey.

County Cork in Ireland is a coastal region in the far southwest with an exceptional microclimate not found anywhere else in Ireland, with warm summers and mild winters. The region has one of the mildest and most temperate climates in Western Europe.

The Cork coast warmed by the Atlantic ‘Gulf Stream’ which results in lush almost tropical, vegetation. Temperatures here tend not to get as low as elsewhere in Ireland – snow is almost unheard of and although it rains more than average, it is also warmer and sunnier than average for Ireland. Temperatures below 0°C (32°F) or above 25°C (77°F) are very rare in County Cork

The effects of this warm, wet, temperate microclimate are immediately evident when you visit County Cork and see palm trees, luxuriant sub-tropical vegetation and exotic flowers growing in abundance in tropical display gardens. Plants such as Italian Casita and actual Palm trees that would find it impossible to survive in other parts of Ireland thrive in County Cork. Another plant, Fuchsia Magellanica, has become the unofficial emblem of the region.

There’s something restorative about the temperate Cork climate that allows subtropical plants to flourish where they have no business growing!

Unlike anywhere else in Ireland, County Cork is ‘a place apart’ and you can taste the difference in HYDE Single Malt Irish Whiskey.


The maturation in oak casks accounts for 80% of the final flavour of HYDE Irish Whiskey.

The wooden barrel type and aging period provides varying flavours, depending on how long it is aged, the type of warehouse used and even the location and orientation of the barrels within the maturation warehouse.

The final flavour from the wooden cask depends on variable such as the origin of the oak, the casks’ previous use and number of uses, cask size, stave width, stave conditioning, maturation environment and the ‘toasting’ or ‘charring’ level before filling.

There are at least six distinct types of vanilla aroma that can be imparted by an oak cask and it takes a ‘good six years’ for these flavour notes to become fully infused into the whiskey.

Whiskey that has matured for at least six years will have more pronounced vanillas and other barrel notes like; maple butterscotch, brown sugar, caramel, ginger, clove, toffee, cinnamon, nutmeg, orange, graham cracker, walnut, almond, butter, anise, bacon, toasted nuts and many, many more!



Licensed under Public Domain via Wikimedia Commons

There are five primary chemical constituents
in the Oak which effects whiskey maturation;


As the name suggests, this compound is primarily composed of a form of glucose (sugar). Despite this, it does not impact on any notable flavour elements in a mature spirit, but instead acts as a binding agent or polymer to help hold the wood together. (i.e. essential in oak’s ability to hold a tight cooperage). It is so effective at its job that it is the most abundant polymer in the natural world.


While also a sugar based polymer, hemicellulose is not solely composed of glucose like cellulose but of multiple sugars such as glucose, xylose, mannose, rhamnose, arabinose and galactose. Most importantly, these sugars are much more unstable than glucose, allowing them to breakdown into their individual parts when stimulated by dramatic changes in their environment, such as heat. In these newly activated hemicellulose sugar condensation by-products (furfural, Hydroxymethylfurfural, maltol and cyclotene) which ultimately give us the deep brown colours and subtle almond, walnut, butter and maple notes from a lightly toasted cask.  When the heat is turned up even higher to the levels of charring, most of these flavours are pushed aside by rich caramel and toffee. For hemicellulose to begin converting into colour and flavour, it needs to be activated by a heat of at least 140°C (284°F) which is why we flame-char the inside of each cask.


Anywhere there is a hardwood, there is lignin. While also a polymer, lignin is composed of two core structural parts; guaiacyl and syringyl. It is the direct result of these combined parts which is responsible for giving us sweet and spicy aromas, especially vanilla, which is pulled from its chemical namesake – vanillin. Lignin congeners can be released very easily with only the smallest amount of activated heat, however it is the effect of heavy toasting and deep charring which breaks down the lignin further into steam volatile phenols, responsible for delivering smoky flavour elements.


As the name suggest, it is from tannin we first derived tanning agents for leather and early dyes, giving us the common word ‘tan’. While there are many different sources of tannin in the natural world (such as grape skins), oak tannins are unique in that most of them can be broken down by not by adding heat, but simply by adding water. For this reason, oak tannins are classified as hydrolysable.

Acting primarily as a means of food storage for the tree, tannin help to protect it from fire and bacteria, evolving into a natural, bitter deterrent to insects in a similar way to the coffee plant (Coffea) produces caffeine as a bitter pesticide. As a hydrolysable compound, seasoning is used to remove large amounts of bitter tannin from the oak prior to cooperage. That said, we still need a small element of tannin to supply us with oxidization and fragrances like cooked apple. More importantly, however, is the role tannin plays on long maturation. The wood chemicals react slowly with oxygen molecules in the spirit over time, creating new compound called diethyl acetal. This new compound ensures that whiskeys of ten years and more such as HYDE are left with rich and complex top notes and are never flat and insipid.


Unlike the above components, lactones are released in the first year of aging and as such are more important to the brand new American whiskey barrels. Neither a polymer nor a sugar compound, lactone is a flavour element influenced by certain oils, soluble fats and waxes simply known as lipids which deliver a unique coconut-woody taste to a spirit. While present in all types of oak, lactones are found in their greatest quantity in American White Oak (with the exception of the rarely used Asian variety Quercas mongolica), releasing almost all of its flavour attributes in the first year of a first-fill barrel’s maturation. For this reason, Bourbon, Tennessee and Rye whiskeys all have outstanding vegetal characteristics when compared to Irish whiskey, which depends more on sweet, smooth polymers for flavour. Well-seasoned and lightly toasted casks can release further amounts of lactone when deep alligator charring can react the other way, reducing its effect.




The Composition of Oak and an Overview of its In?luence on Maturation – c/o





During cask production, the inside of a cask can be ‘Toasted’ or ‘Charred’ over an open flame or over an oven. Toasting is carried out before charring and takes place, slowly, over a longer period of time with a small flame. When toasting, the flame DOES NOT come in direct contact with the wood inside the cask.

Toasting releases vanillins from the natural cellulose in the wood and breaks down chemicals in the wood such as lignin, cellulose and hemicellulose to create different flavours and aromas imparted from the cask.

This gentle ‘toasting’ process mellows the natural tannins in the wood, as well as changing the angular flavours which the barrel might impart from the raw wood. This gives a smoother, spicier, whiskey with lingering vanilla flavour notes.

There are varying degrees of ‘toasting’; from a light toast to a heavy toast. As you might imagine, each level has a varying influence on the final whiskey taste. Essentially, the heavier the ‘toasting’, the stronger the final flavour impact from the oak cask.


Charring is a shorter more intense high heat process where the naked flame actually makes direct contact with the inside of the wooden cask for about one minute. This causes the wood to ‘char’ on the inside of the cask, causing it to crack open.

The word ‘charred’ implies that something has gone past toasting to a partially burnt state, and indeed charred barrels look black on the inside. They are about an eighth of an inch or 3.175mm charred.

This flame ‘charred’ wood also behaves as a natural activated carbon filter layer, which helps remove nasty tasting sulphur compounds from the original ‘new fill’ whiskey, to produce a smooth final whiskey taste. Flame ‘Charring’ the cask cracks also opens the wood surface allowing the whiskey to penetrate the cask staves to impart a darker final colour with smooth flavour notes of caramel and honey with spicy overtones.