About Whiskey Distillation
By Richard Thomas
I’m sometimes surprised by how little so many lovers of whiskey know about distillation until they make their first visit to a distillery. Until that visit, distillation is an almost magical liquor-making process involving almost medieval equipment and ancient techniques. Distillation is an ancient process, but there is nothing magical about it. Instead, distillation is the science of separating substances based upon their different boiling points. The usual purpose of separating those substances is to selectively concentrate one of them, and in the case of a whiskey still the point is to concentrate the alcohol.
The alcohol in all whiskey is created by fermentation, not distillation. Whether it be corn, winter wheat or malted barley, the starch in the grain is converted to sugar, and then the sugar is fermented into alcohol by yeast. What comes out of fermentation typically has an alcohol content of between 5 and 7%, a far cry from the usual minimum content for whiskey of 40% .
Ethanol, the kind of alcohol found in both your fine bottle of scotch and the “gasahol” most people in the Western Hemisphere pump into their cars, boils at 173.3° F (78.5° C). Water, the other main liquid in a whiskey mash, boils at 212° F (100° C). A still is essentially a “cooker” and a condenser. The cooker heats up the liquids to the point where the alcohol boils off, but the water and other impurities remain. The alcohol vapor then rises out of the cooker and collects in a condenser, where it cools, resumes liquid form and collects.
Distillation is not perfect, however, and the level of purity a whiskey-maker is allowed to achieve is usually determined by national law. Bourbon-makers are not allowed to distill their liquor past 80% alcohol content, while scotch has a limit of 94.8%. Achieving high concentrations of alcohol usually requires more than one trip through the still. Double distillation is the norm for scotch, while triple distillation is not unusual in Ireland.
On a distillery tour, I inquired about how the level of concentration and purity in the alcohol whiskey-making, and what he said answered my question without revealing anything about his own process: “I’m allowed to distill my whiskey up to 80%, which means that other fifth is something else. If I distill it to less than that, I get more of that other stuff.” Little tweaks in the distillation process might make a big difference in the end product, making the distillation stage as important as the grain recipe, the yeast or the aging.
Another misconception about distillation is the importance of copper. Copper stills are beautiful and certainly embody the whole tradition of whiskey-making, but the difference between copper and stainless steel in terms of distillation is about the same as it is in your cooking pots. Copper is a better conductor of heat, but it is also very expensive, and not as strong as steel. Copper also catalyzes certain undesirable trace compounds formed during fermentation. So, a copper still is more efficient and has some desirable qualities, but a copper still also must be built much heavier than its stainless steel equivalent, and is considerably more expensive. For this reason, many mass market whiskeys are made in stainless steel stills. Overall, copper is the best material for building a still, but that doesn’t make stainless steel bad, and sometimes too much is made of the difference.
Stainless steel and copper both show the same peaks, valleys and proportions when the distillate is examined through a gas chromatograph, however what the GC machine does not measure are the intangibles…which is a copper still used for whiskey making yields a better flavor oppose to a stainless steel method. The read outs from a GC machine may show identical proportions and detect the presence of the same ethers and so forth, but what it does not “print out” is how it tastes. Since the article is referring to specifically the use of copper and how it is no more advantageous than the use of stainless steel, it must be important to note the only thing that matters is the flavor profile of the finished product..In other words, what we spend 60 dollars on in the liquor store. Considering copper does in fact give the whiskey maker a much better quality spirit, I’d say copper makes all the difference in the world.