Ahh, “smooth”. Spirits aficionados react to the word the same way just about everybody reacts to the word “moist”: with visible discomfort and a quick change of subject. Coined by some college kid somewhere, no doubt, the word is generally used to refer to a high-proof spirituous beverage that does not make the drinker gag or cringe when shooting it. Hardly a ringing endorsement, yet it’s often employed as the default compliment for any drink foisted onto a person by a well-meaning friend.
This college-kid mentality is easy to understand, however; After four (or five? Or six?) very long years of being forced to drink shots of the cheapest (read: worst) possible booze, one could be forgiven for holding “doesn’t make me gag” up as the pinnacle of achievement in spirits craftsmanship. Indeed, this one (of many) attributes of quality liquor is probably the first thing that attracts the newly-minted spirits lover into the wonderful world of good booze.
It takes quite some time and experience before one begins to mentally separate alcohol “heat” from low-quality “roughness”, which are often both confused to mean “not smooth” in the collegiate vernacular. In other words, a high-quality well-aged single malt can be a fiery 70% alcohol (140 proof), which could rightly be described as “very hot”, and yet not result in that spine-shuddering, head-shaking, eye-squeezing, throat-tearing sensation that plagued your university years. Conversely, the cheapest $10 handle of vaguely Russian-sounding vodka can be watered down to 30% ABV (quite the opposite of “hot”) and still be awful to shoot. My stomach turneth over at the very thought.
So what causes things to be “smooth” or “rough”? While there are likely several very scholarly works on the subject, this isn’t that kind of blog and you’re simply going to have to go with what I dredged up from the Internet. Just be glad I passed on (most of) the memes, and take my advice and never Google Image-Search the word “smooth”. While we’re on the subject, never search “moist” either. Just don’t do it.
I’m going to categorize the things that lead a drink to be “smooth” into three categories: 1) Craft, 2) Additives, and 3) Technique.
The most noble way to make a drink “smooth” comes down to the craftsmanship of its production. If quality ingredients are distilled skillfully in quality stills and aged in quality oak barrels for a sufficient quantity of time, one can expect a degree of “smoothness”. This is due to several factors: alcohol by-products formed by the fermentation of sugars (or starches that are malted into sugars) contain some nasty stuff in low quantities that is concentrated during distillation. These “heads” and “tails” are removed by the still operator. This is referred to as the “cut”, and a skillful “cut” can remove the worst offenders while leaving in the best flavor and aroma compounds. A “wide” cut which leaves more of this stuff in can reduce the costs of production, but also keeps the shudder-inducing flavors of industrial oils, bitter grassiness, solvents and adhesives, and rotting fruits. Note that cuts only really apply to pot stills, while most spirits (especially most of the cheaper spirits) are made on a continuous column still. The “cuts” are a lot more complicated and technical with a column still, and involve adjusting the plates inside the still. Suffice it to say a column still is still capable of making cheap booze with off flavors, even without wide cuts. When spirit leaves either type of still, it naturally has a number of off-tasting compounds which can be removed or converted by a number of procedures. Filtering through charcoal or other media can do this (hence the proliferation of the word “filtered” on every vodka label, ever), as can aging in oak (the voodoo of oak maturation is a subject for another time, but oak both filters and converts off-flavors into tasty ones while simultaneously adding its own compounds). Running the spirit through a still such that it comes into contact with a lot of copper also removes off flavors such as sulphur by binding them with available copper ions. You want copper sulfate to stay behind in the still, not show up in your bottle.
It turns out that in the pursuit of the “Fake ID” market, alcohol producers have a number of options of additives to simulate the “smoothness” of more-expensive products, without resorting to the age-old, inefficient, and costly maturation in oak. First and most obvious is water. Most spirits in most countries have a legal definition that requires them to be at least 40% alcohol by volume (ABV), and this is achieved by the simple process of adding water. However, some legal definitions of things like “spirit drinks” or “liqueurs” allow lower alcohol concentrations, and thus more “smoothness”. As we discussed above, high ABV does not necessarily translate to roughness, but if the spirit is cheaply made and/or unaged, water will certainly help. The second additive is sugar. Sugar does a great job of masking off-flavors (just look at the nutrition label on any processed food) and is cheap. Pre-mixed drinks, liqueurs like triple sec or schnapps, and many flavored vodkas or whiskies contain sugar along with the flavorings for this reason. A third common additive is glycerin. Glycerin is a “natural” byproduct of soap making, and although it is colorless and flavorless, it adds “body” to drinks and softens rough flavors, which tricks tastebuds into thinking the spirit is “smooth”. Most drinks with legal definitions (like single-malt scotch or bourbon) cannot contain added glycerin or other additives, but other, cheaper, drink categories can.
Lastly, the way in which you drink your spirits can affect your perception of “roughness” or “smoothness”. Ice is an obvious example. “Well” vodka at many watering holes is one of the cheapest, nastiest distillates you can find, yet chill that poison down via vigorous shaking with ice and add a drop of vermouth and it can be palatable (notice I didn’t say good). Of course, the adding of mixers (usually containing sugar) is the trifecta of smooth-making… uhh… -ness: Sugar to sweeten, water to dilute, and strong flavors to mask. Finally, avoiding the shot itself can help turn a “rough” spirit into a “smooth” one: sip the liquor, hold it in your mouth for several seconds while your powerful saliva enzymes work on it and it anesthetizes your tongue, and then swallow it. For more, see my article on How to Taste Scotch (or whisky).
Regardless of what occurred between grain and shot glass, you should be warned that the term “smooth” will get you nowhere with the snootier whisky-appreciating crowd. Considering the myriad ways that spirits can become “smooth”, and the fact that most of them either involve adulterating the original ingredients or removing good flavors and textures along with bad, the term is frowned-upon by the aforementioned snoots. “Adding water and ice to ‘Jack makes it smooth too”, they might say, or “so are wine coolers” (ouch). Putting aside the fact that saying something like that immediately makes a person into a giant jerk, if you’re still using “smooth” to describe whisky, you might want to reconsider in certain crowds. Yes, that 30 year-old whisky is indeed smooth, but you might want to go with “supple”, “creamy”, “silky”, or “soft” (thank you Thesaurus.com!), if only for appearance’s sake.