By law, straight American whiskeys must be entered into the barrel for ageing at no more than 62.5 per cent abv. Although some whiskey-makers age their bourbons at exactly this proof, a handful of distillers bring their new spirit down to as low as 55 per cent abv before barrelling. Not surprisingly, their accountants often find this goes against their grain.
Diluting before ageing means that more barrels are needed, as well as more space in the warehouse and manpower to stack them. Generally though, this practice makes better whiskey. Both Maker's Mark and Wild Turkey distilleries, for example, dilute their spirit before ageing, and they consistently issue great bourbons. The best whiskeys from distilleries that enter their whiskey at maximum strength tend to need to spend longer in the wood before they reach their prime. Indeed, tests have shown that after eight years of ageing, one whiskey barrelled at 54.5 per cent abv gained almost 50 per cent more colour than whiskey barrelled at 77.5 per cent abv, and the first whiskey also contained more desirable esters than the latter.Barrels
US law requires that all straight whiskeys must be aged for a minimum of two years in new charred oak casks. Four years is the norm and any whiskey aged for less than four years must declare that fact on the label. The rule about new barrels initially had nothing to do with the whiskey-making process. It was the result of lobbying by Arkansas congressman Wilbur Mills who, when the 1935 Federal Alcohol Administration Act was being written, did his best to ensure a steady business for Arkansas – a state that grows many oak trees.When each distiller orders his new charred casks, he decides how much char is burned into the inside of the barrel. Cooperages generally offer char levels of one through to four, each differing by mere seconds of burning, resulting in depths of char that differ by minuscule fractions of an inch. Each has a distinct impact on flavour.During the ageing process, whiskey undergoes three types of chemical changes. First the whiskey extracts constituents from the wood, then the components in the original whiskey, plus the wood constituents that have been drawn into it, oxidise over time. Lastly, reaction between organic substances in the spirit results in new congeners in the whiskey.And although it's hard to pinpoint which depth of char is responsible for which changes in ageing, whiskey aged in barrels bearing differing levels of char react differently to the ageing process. Jim Beam and Wild Turkey are probably the only distilleries that order the deepest, level four char, and their whiskeys tend to display a boldness of character, even at relatively early stages of their maturation.The red layer
While the whiskey slumbers in the wood, individual master distillers use an assortment of different ways to control their warehouses and deal with the barrels resting there. Indeed, it is at this point of the whiskey-making process that there is a chance to alter what's in the barrel without actually adulterating it.Because temperatures in Kentucky, along with those in Virginia and Tennessee, are warmer than in Scotland, whiskey matures more quickly. However, other factors are also at work , and none is more important than what's known as the red layer in the new charred oak casks. A layer of caramelised wood sugars is created when the cask is toasted, prior to being charred, and it lies just beneath the char itself. When temperatures rise during the summer months, the whiskey expands into the red layer gaining both colour and flavour. During the cooler weather, when the whiskey contracts, these new aspects are introduced to the whole barrel. Some distilleries, though, create false seasons by heating their warehouses during wintertime, allowing the temperature to rise for a few days, then turning off the heat for a while so the whiskey goes into, and out of, the red layer a number of times. This practice is not regarded as cheating and, indeed, it dates back over a century. Yet although it does have a positive effect on the whiskey, there is no true substitute for time.In the warehouse
The warehouses where most bourbon whiskeys age are, in true American style, skyscrapers in comparison to the usual single-storey ageing houses in Scotland, although there are exceptions on both sides of the Atlantic. In the heat and humidity of Kentucky and Tennessee, this can cause a problem, as the barrels on the top floor, sometimes as high as 12 storeys, age far faster than those at ground level, where it is cooler. Many distilleries simply use the standard practice of mingling together barrels from various floors of the warehouse to produce specific bottlings, so sometimes whiskey aged for four years at or near the ground level, is married to whiskey from the top floor to make it palatable. The resultant mix is then usually bottled as a low- priced brand. Some distilleries use whiskey that has matured solely in specific so-called sweet spots in the warehouse – usually around the fifth to seventh floors – to make their top-of-the-range bottlings.The other way to deal with warehouse temperature fluctuations is to rotate the barrels periodically, so that each one spends time at various temperatures. This practice is labour intensive, and therefore expensive, but some distillers go to the trouble, and this is reflected in the consistency of their finished product.The colour
Although not widely practised, it is legally permissible to add a certain amount of caramel to Scotch in order to alter its colour. The same is true of cognac. Straight American whiskeys, however, cannot, by law, contain any added colouring. Therefore, what you see is what you get - all of the colour in a bottle of bourbon whiskey is directly attributable to the ageing process.Filtration
The words 'charcoal filtered' appear on many bourbons , and usually they refer to a filtration through activated carbon that occurs after ageing and prior to bottling. Neither activated carbon, nor diatomaceous (powdery) earth, the other commonly used filtration agent, does anything more than remove certain congeners in the whiskey that can result in what's known as a chill haze – or simply cloudy whiskey – should the spirit get too cold.This filtration is necessary only in whiskey that will be bottled at under 50 per cent abv, since at higher proof a chill haze will not occur. This is evident in one bottling, Booker's Bourbon, bottled at barrel proof, usually around 61 per cent abv, which undergoes no filtration whatsoever.
Many distilleries chill their whiskey, sometimes to as low as 20 degrees Fahrenheit, prior to filtration, to ensure that every single congener that can cause a chill haze is removed. A few whiskey-makers, though, filter at room temperature. This practice is far preferable since the whiskey will not become cloudy at low temperatures, and more flavour is retained in the spirit. Tennessee style
Although not legally bound, the two Tennessee distilleries, George Dickel and Jack Daniel's, abide by a traditional method of producing whiskey. It involves a peculiar form of filtration known as the Lincoln County Process. Although it's illegal to add flavouring to straight American whiskey, these wily Tennesseans have found a way around the law that dates back to the early 1800s.It is said that Tennessee distiller Alfred Eaton was the first to make charcoal from sugar maples then filter his whiskey through it as soon as it came off the still. This process, which is carried on to this day, has a substantial effect on the flavour of the whiskey. The process does seem to add a distinctive sweet sootiness to the whiskey, as many testify who have tasted Tennessee whiskey from both distilleries straight off the still, and then again after it has passed through the huge vats filled with sugar-maple charcoal. Just enjoy
America has always been driven by profit and progress, and the same is true for the American whiskey industry. But although companies are out to make a profit – just as the Scots and Irish distillers are – tradition is vitally important too and often carries sway over cost-effectiveness.
If you're new to this category of whiskey, don't start comparing it to your favourite dram of Scotch. Take it for what it is, sample a few different bottlings, make yourself a Manhattan, and soon you'll be whittling your own stick, just rocking on the front porch a-watching the neighbour folk pass by.