Introduction
Here, in Part 1 of Saved by the Staves, I focus on the history of the wood barrel and the tremendous influence oak maturation exerts on the flavor profile of Scotch whisky. The upcoming Part 2 of Saved by the Staves (Column No.11 of A Rich Pour) will examine what transpires once a Scotch whisky has reached maturity, and will also take a look at some noteworthy cask-strength single malt editions.
Merely an overture
They say, “The first time is the best time.” Well, in the case of Scotch or, more specifically, cask-strength single malt, I’m not so sure. Though I still remember my initial pour of straight-from-the-barrel Scotch, many subsequent cask-strength whiskies have proved even more eye-opening. Clearly, that first encounter was merely an overture to a long, satisfying and as yet – thankfully – unfinished symphony.
Those first few pours of cask-strength Scotch can be truly memorable,
as with this powerful and elemental version of Islay’s Caol Ila.
There are numerous reasons to celebrate cask-strength single malt Scotch and the wondrous way in which it evolves during its years spent in wood. Let’s begin by peering through the historical looking glass to search out the roots of the relationship between wood and whisky.
An old bond
The bond between wood and whisky (or whiskey) stretches back in time and encompasses many regions of the globe. Ireland, Canada, the United States of America and Japan – to name but a few countries – boast strong traditions in the ageing of the noble liquor in wooden containers. Yet it is the tiny nation of Scotland that has adopted the most eclectic approach of all in terms of the variety of vessels used to mature its spirit in – perhaps not surprising given the Scots’ reputation for thrift and the fact that the great old-growth stands of trees once adorning the native landscape now represent little more than a vanished forest of Scottish lore. While the whisky may flow as magnificently as ever, it passes – by and large – into imported oak.
Oak provides a perfect medium for mellowing and embellishing the rather aggressive spirit that condenses off a typical whisky still. How aggressive? A few years ago, Bruichladdich Distillery, on the Isle of Islay, carried out experimental replication of a 17th Century quadruple-distilled whisky mentioned in the writings of one Martin Martin. In the olden days, the science of distillation was an imprecise one at best, and much of the whisky so crude as to require the addition of herbs, spices and sometimes sweeteners to render it palatable. Aqua vitae became aqua composita. Even more worrisome was the potential presence of methanol. Martin needn’t have feared poisoning from his Isle of Lewis dram, as the four-times-over distillation utilized likely removed any residual methanol. However, the after-effects of that particular whisky were aptly reflected in its name, usquebaugh-baul, which is Gaelic for ‘perilous whisky’. Evidently, Bruichladdich’s 92% alcohol by volume recreation of usquebaugh-baul also achieved notoriety, as even the Defence Threat Reduction Agency, a security arm of the Government of the United States of America, kept an eye on the Islay site’s webcams lest the distillery were producing chemical weapons. The Americans might have been onto something.
The typical fresh-from-the-pot-still single malt Scotch of today, whether double or triple-distilled, doesn’t pack quite so perilous a punch. And it’s doubtless a purer potion than much of what passed for whisky in the days of old. But you probably wouldn’t want to lay your lips to it, given the high alcohol content, immaturity and sheer intensity of the spirit. Time for those wooden vessels to work their magic.
The enduring craft of the cooper
Casks have been around for a long, long while, the earliest examples dating back at least two millennia. Wood constituted and remains one of the most readily available and easily workable materials. Casks originally served to replace tightly woven baskets for purposes of safe storage and transport of liquids. It’s not surprising, then, that the term ‘cooper’, used to describe one who constructs barrels, derives from ‘coop’, which once connoted a basket specifically made for holding chickens.
During the period of the Roman Empire, the original method of awkwardly hollowing out sections of tree trunks to make barrels was superseded by the more sophisticated piecing together of individually hewn staves, or curved boards. A good portion of these barrels were used to store beer. By the 3rd Century A.D., barrels also became the containers of choice for shipping wine from the vineyards of Bordeaux and Germany to the monks residing in the British Isles, and the ancient amphora was thus largely discarded.
The stave has proved an ingenious and enduring
concept in the fabrication of wood barrels.
As the Middle Ages rolled around, coopers’ guilds and taxes on the lucrative barrel business became realities. Coopers of that era and of later times assembled barrels not only for the cognac, whisky, wine and beer trades, but also for the fisheries and other industries. The thought of whisky being racked into a used herring barrel might not sound too appetizing, but such a practice likely occurred, be it accidentally or intentionally, on more than one occasion – talk about marine scents! In Scotland, smugglers grew extremely fond of the smaller (approximately 12 gallon) quarter cask, as it facilitated both transport of illicit whisky by horse and evasion of the Excise men. (Laphroaig Distillery recently resurrected use of the quarter cask for one of its bottlings.)
The making of casks exclusively with hand tools persisted through to the middle of the 19th Century, when machinery for fabricating staves as well as for assembling barrels was finally developed. Notwithstanding the ancient, established use of wood for storing and shipping of beverages, it was only around this same time that distillers and purveyors of whisky began to realize the true value of ageing their spirit in oak. Mouth-puckering power and rawness, the latter already lessened to some degree by evolutionary refinement of the copper pot-still, gave way to more mature and mellow characteristics, and casks suddenly grew worth far more than their weight in whisky. In another happy coincidence, the Scotch houses and merchants happened to be blessed with a readily available and relatively inexpensive supply of casks from the Madeira, Port and Sherry trades. These casks imparted added roundness and richness to the spirits. Distilleries and their associated cooperages could now be found all over the countryside, and stockpiles of whisky in wood soared to the warehouse rafters, increasing six-fold in less than a decade.
This Port cask may one day be destined to hold whisky.
Today, after a century of rationalization and belt-tightening within the Scotch whisky industry, the dedicated distillery-based cooperage has become a rarity in Scotland, and the art of making and repairing casks is carried out mostly by commercial specialists such as Camlachie Cooperage and Speyside Cooperage. What’s more, the increasing cost and dwindling supply of fortified wine vessels from the Iberian Peninsula has forced the Scots to look elsewhere for much of their wood – America.
There’s oak, and then there’s oak
Oak reigns as the pre-eminent wood in which to age spirit. Its dense structure and durability, as well as its ability to impart positive aromatic and flavor traits, count as valuable attributes. But not just any oak will suffice. In fact, only a couple of varieties stand out – Quercus alba, known as North American white oak, and Quercus robur, variously called European, English or pedunculate oak. When harvested in their prime, carefully cut into boards in small-yield manner so as to minimize potential leakage, and air or kiln-dried to a low residual moisture level, these two types of oak offer the ideal raw material for fashioning quality casks. In the real whisky world, however, use of North American white oak far outstrips that of the European variety.
A shapely form
Construction of an oak cask starts with the graduated tapering and edge angling, as well as the cutting of lateral grooves in both ends, of each of the individual boards, or staves. The grooves will eventually form a pair of indented rings at either end of the cask, called crozes, into which circular heads will be fitted. The staves are then aligned in a circle with the aid of a jig, heated and/or moistened, and bent to form the shell of the cask-to-be. A series of hoops, ranging from the bilge hoops near the center through the quarter hoops to the head hoops at the two ends, are forced into their respective locations and riveted. These hoops serve to hold the staves firmly in place. The end-most head hoops, though, are only tamped into their final positions following insertion of the heads.
The barrel begins to take form,
in this case over flames.
How do you like your ‘toast’?
A key decision in the cask-making process centers around whether or not to toast, or flame-sear, the inside surfaces of the oak vessel, and if so, to what extent. Why would anyone in their right mind wish to burn high quality oak? For spirits producers, toasting offers definite advantages. As the flames begin to scorch the oak, they both sterilize and break down the surface, thereby creating three distinct strata – a charcoal layer on the inside where the flames have charred the surface, an intact layer on the outside not affected by the flames, and a thin transitional band between the two often referred to as the ‘red’ layer. In a recent twist on an old technique, electric radiant heaters, which purportedly provide more exacting control over the toasting process, have made a limited appearance within the barrel industry.
Toasting not only increases the superficial porosity of the staves; it also precipitates several key chemical changes in the nature of the charred surfaces. Lignin, an essential strengthening component of wood, yields two noteworthy methoxyphenols, guaiacol and syringel, when burned. Guaiacol possesses a vanilla-like taste, while syringel tends to emit scents of smoke and spice. The latter substance is somewhat analogous to the aromatic phenols in peat-reeked Scotches such as those from Islay. Another pyrolytic lignin deriviative, eugenol, exhibits an attractive clove-like fragrance. Hemicellulose, a polymer of sugars, contributes toast and caramel characteristics upon being heated. It can also, in such a state, contribute additional textural body and color to alcoholic liquid it comes in contact with. Tannins may play a significant role in the wood ageing of wines. However, they can also react with spirits to produce aromatic acetals. Tannins tend to be found in higher amounts in European oak. Finally, oak lactones, which occur in more concentrated form in North American white oak, offer up wood and coconut nuances. It’s no wonder, given the breadth of additional aromas and flavors these substances offer, that toasted oak barrels are so valued by certain segments of the spirits industry.
American Bourbon producers actually augment and tailor the degree of toasting to specific whiskies by specifying the depth of searing, now more properly termed charring, from Grade 1 through to Grade 4. Employment of these barrels is, due to the fact that all Bourbon must be matured in new, freshly charred wood, strictly a one-shot deal. Scottish distillers and merchants, in contrast, depend heavily on these very same, now ‘used’ Bourbon barrels, and may fill them with their own whisky two, three or even four times, refurbishing the barrels through scraping and re-toasting of the interior surfaces solely if necessary or when more pronounced wood-derived aromas and flavors are desired. The greatest transfer of wood-derived elements from oak vessel to liquid takes place within a newly fabricated, freshly filled barrel. When the original contents are emptied and another spirit introduced, as occurs when an ex-Bourbon barrel or ex-Sherry cask is filled with Scotch whisky, the vessel is deemed a first-fill barrel or cask. The Scotch whisky maturing in such a container will benefit from the type of oak as well as from the residual influence of the original contents. Subsequent refills will, however, diminish the effects of both wood and prior liquids.
The Sherry cask conundrum
Despite the prevalence throughout Scotland’s distilleries and whisky warehouses of used barrels and reconstituted barrel staves from the United States of America, some single malt producers and purveyors persist in ageing their spirits in Spanish Sherry wood, either partially or totally. Aberlour, Dalmore, Edradour, Glenfarclas, Highland Park and Mortlach, for instance, market editions of their whiskies that benefit stylistically from maturation in wood previously seasoned with Spanish fortified wines – normally Oloroso Sherries made from the Palomino and Pedro Ximénez grape varieties. The Macallan Distillery takes this tact one step further by ageing its ‘traditional’ line of single malts exclusively in first and second-fill casks imported directly, and whole, from Jerez.
The type of wood in which a whisky is aged can make a huge
difference in the spirit’s hue. Here, the Bourbon barrel aged Scotch
on the left appears notably lighter than its Sherry cask aged
counterpart on the right.
Nonetheless, it would be a mistake to presume that all ‘recycled’ Sherry wood is of the Quercus robur, or European, variety. It is not. In fact, a preponderance of the oak vessels resting within the bodegas of Jerez is fabricated from imported American oak, or Quercus alba. Herein rests the challenge of trying to differentiate between the relative effects of wine and type of oak on any given Sherry wood aged whisky. And just to throw another monkey wrench into the equation, producers have been known to rejuvenate well-used whisky barrels by wine-treating them with either Sherry or a concentrated Solera-aged reduction of Sherry, called Paxarete, which possesses a low percentage of alcohol allied with a great deal of residual sugar. Paxarete has not been used for over a decade and a half, though some argue that it should once again be permitted.
Does any of this matter? If you believe spokespeople for The Macallan, which specifies 100 percent European oak Sherry casks for its ‘traditional’ line of single malts, then the answer must be, “Yes.” I feel, however, that micro-adjusting the use of wine-seasoned wood (whether through relative proportion to ex-Bourbon wood or through ratio of first to second-fill Sherry casks) to the unique characteristics of a particular single malt is far more important.
Super-size me
Used wine and spirits casks can be found in a wide variety of pedigrees and sizes. The Scotch whisky trade, given its willingness to experiment as well as its penchant for avoiding wastefulness, takes full advantage of this situation, importing oak vessels from many regions of Europe and North America. Though used Port and Sherry casks, ranging in volume from 450 liter Puncheons to 500 liter or 600 liter (the latter close to 160 gallons) Butts, are prized commodities, it is the 180 liter to 200 liter (falling within the high 40 to low 50 gallon range) American Standard Barrel that forms the backbone of Scotland’s supplies. Until quite recently, the Scots often disassembled ex-Bourbon or ex-Tennessee whiskey barrels at source, then shipped the staves and utilized them to fabricate larger vessels of approximately 250 liters (just over 65 gallons), often referred to as Scottish Hogsheads. Nowadays, however, the trend has swung to importing American Standard Barrels whole and leaving them as-is.
A typical Highland distillery warehouse filled close to the rafters with whisky.
Why is so much attention paid to cask size? Efficient warehouse space usage and ease of cask movement certainly favor sensibly sized vessels over larger ones. More importantly, however, the ratio of internal cask surface to volume of whisky proves critical in determining an ideal period of maturation, with smaller casks generally ageing their contents faster. Rapidity of ageing isn’t the be-all and end-all, though, and distillery managers try to fine-tune rate of maturation to the style of whisky while simultaneously taking the economics of storage and turnover into consideration. For Scotch whisky producers, the 180 liter to 200 liter American Standard Barrel and the 250 liter Hogshead offer sage compromises between all of the above-mentioned factors.
Change for the better
Wood ageing of whisky changes the chemical composition as well as the aroma and flavor of the spirit, particularly during the early stages of maturation when many of the less attractive traits of the fresh distillate diminish dramatically. This phenomenon is often referred to as subtractive maturation. Concurrently, intermingling of oak and liquid embellishes the whisky with desirable elements. This process is known as additive maturation. Interactive maturation, which entails gradual melding of age-acquired aspects as well as diminution of very pronounced distillate characteristics, becomes more important following the first 3 to 5 years. After a certain amount of time, the whisky will begin to display a harmonious integration of its different scents and tastes, and from this point on distillery or company personnel will keep a watchful eye on the slumbering spirit with a view to deciding when to bottle.
But when will the whisky awake?
Something gained, something lost
During maturation, variations in temperature and humidity cause expansion and contraction of the pores of the oak cask as well as the spirit within. These climatic changes facilitate the ongoing exchange of compounds between wood and whisky. Alas, they also lead to increased evaporation of the whisky through the wood. In Scotland, as opposed to Kentucky or Tennessee, the evaporation of alcohol continuously outpaces that of water, resulting in a loss of both volume of liquid and percentage of alcohol. Warehouses fill with the fragrance of distilled grain spirit even as local air penetrates into the casks. Though the debate over whether or not local ambient conditions have much of an effect, if any, on whisky ageing away in cask continues unabated, I cannot help but suspect that they do – especially in the case of distillery warehouses sited at high altitudes or near the sea.
If air can penetrate a cask, then
why can it not also influence flavor?
More to come
Please stay tuned for the upcoming Part 2 of Saved by the Staves, as I turn my attention from barrels to bottles and explore the wonderful world of cask-strength single malt Scotch whiskies. I can practically guarantee you’ll be thirsty for a dram after reading it!
Referenced articles / books / websites
Conner, John M.; Paterson, Alistair & Piggott, John R. “Changes in wood extractives from oak casks through maturation of Scotch malt whisky”, Food Science Laboratories, Department of Bioscience and Biotechnology, University of Strathclyde, Glasgow, UK, Journal of the Science of Food and Agriculture, Volume 62 Issue 2, pages 169-174, ©1993 John Wiley & Sons, Ltd.
Conner, John; Reid, Ken & Jack, Frances. “Maturation and blending”, Whisky: Technology, Production and Marketing, Chapter 7, pages 209-237, Volume Editor: Inge Russell, part of the Handbook of Alcoholic Beverages series, Academic Press, London, UK, ©2003 Elsevier Ltd.
Gordon, Grant E. "Marketing Scotch whisky", Whisky:Technology, Production and Marketing, Chapter 10, pages 309-349, Volume Editor: Inge Russell, part of the Handbook of Alcoholic Beverages series, Academic Press, London, UK, ©2003 Elsevier Ltd.
Kuebler, Doug. The Tumbler’s Guide to Single Malt Scotch Whisky: Armchair Reference Manual & Field Guide, Topeda Hill Publishing, Inc., Baldwin Mills, Québec, Canada, ©2003 Doug Kuebler & Topeda Hill Publishing, Inc.
Martin Martin, Gent. A Description of the Western Islands of Scotland (circa 1695), First Edition 1703, subsequently republished in the 20th Century, edited with an introduction by Donald J. Macleod, O.B.E., M.A., D. Litt., Officer d’Académie, www.appins.org/martin.htm
Nicol, Denis Arthur. “Batch distillation”, Whisky: Technology, Production and Marketing, Chapter 5, pages 153-176, Volume Editor: Inge Russell, part of the Handbook of Alcoholic Beverages series, Academic Press, London, UK, ©2003 Elsevier Ltd.
Piggott, John R.; Conner, John M.; Paterson, Alistair & Clyne, Janice. “Effects on Scotch whisky composition and flavour of maturation in oak casks with varying histories”, University of Strathclyde, Glasgow, UK, International Journal of Food Science & Technology, Volume 28 Issue 3, June 1993, pages 303-318
Stockwell, Tim, Ph.D.; Leng, Jiali & Sturge, Jodi. “Alcohol Pricing and Public health in Canada: Issues and Opportunities”, A Discussion Paper prepared for the National Alcohol Strategy Working Group, February 2006, ©2006 Centre for Addictions Research of BC, University of Victoria, British Columbia, Canada
Twede, Diana. “The Cask Age: the Technology and History of Wooden Barrels”, Michigan State University, School of Packaging, East Lansing, Michigan, U.S.A., Packaging Technology and Science 2005, Volume 18, pages 253-264, published online June 13, 2005, Wiley InterScience, www.interscience.wiley.com
Van Meersbergen, Michel. “E-pistle 2007/050 – Paxarete, the unloved saviour of sherry casks?”, Malt Maniacs, Issue No.105 – Whisky Writings, August 1, 2007, Editor: Johannes van den Heuvel
Waterhouse, Andrew L. and the students of VEN219, “Composition of Oak”, Natural Products of Wine, Department of Viticulture and Enology, University of California, Davis, California, Spring 2001, ©2001 Andrew L. Waterhouse and UCD Students of Natural Products of Wine, http://waterhouse.ucdavis.edu/ven219/index.htm
“History of the Seagram Plant in Waterloo: Making Fine Products – Barrel Warehouses”, www.city.waterloo.on.ca/SeagramCollection
“Scottish distillery makes ‘perilous’ dram”, CBC News, February 28, 2006, www.cbc.ca
“Sherry; ‘Spanish Oak’ – which is it?”, the Scotch blog, September 5, 2006, www.thescotchblog.com
“The Maturation of Whisky in Casks”, The Whisky Store, www.thewhiskystore
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