Swirling Your Spirit Exposes its Quality
Swirling Your Spirit Exposes its Quality
Myth: Swirling is an essential part of the spirits nosing and evaluating process. However, tulip nose-cannon glass users will tell you not to swirl because it releases the ethanol alcohol. For decades, that bit of advice has kept millions of spirits drinkers in the dark about what is really hiding in their glass. If you can’t get the aromas out of the glass, you will never know the quality. As a matter of fact, the uneducated whiskey drinker believes the strong pungency of ethanol is the quality. Most drinkers have no idea that swirling also releases all aromas. To put it differently, quality is not all good: There is good quality and poor quality.
No Swirling = No Evaporation = No Smell.
Swirling enhances evaporation by releasing more aromas to the vapor cloud for detection. Practice vigorous swirling to create more evaporation consequently more aromas. Swirling is one more reason why tulip glasses don’t work well when it comes to delivering character aromas and flavors. Notably, they are simply too narrow to swirl well.
Swirling Science
Two scientific principles describe the effect of swirling. The first is boundary layer. Boundary layers form where a liquid meets the atmosphere. Within this very thin region, evaporating molecules accumulate above the surface and create concentration, temperature, and velocity gradients. Diffusion moves vapor through the layer, while air currents and convection carry it into the surrounding atmosphere. Temperature, airflow, surface area, and molecular volatility determine how quickly this exchange occurs.
Boundary Layer Science
Swirling disrupts the spirit’s boundary layer and spreads a thin liquid film across the glass, greatly increasing the exposed surface area. The motion continuously replaces the saturated air above the liquid with less-saturated air, accelerating the evaporation of ethanol, water, and volatile aroma compounds. Consequently, when swirling stops, vapor accumulates again above the surface and the boundary layer gradually reforms.
Surface Tension Science
To put the issue in perspective, every liquid has an invisible force at its interface with the atmosphere (air) called surface tension. Additionally, did you ever wonder why a water bug can walk on the surface of the water without falling in? Surface tension keeps the water bug on the water surface. It also keeps aroma molecules in the liquid of a spirit or wine. Accordingly, swirling breaks the surface tension, allows aromas to escape and enhances evaporation. Large drinking glass bowl diameters increase the wetted sidewall area, improve swirling velocity, and release more aromas. Swirling height = more wetted sidewall area = more evaporation. For this reason, we debunk the “don’t swirl spirits” myth.
Geometry of the Swirl
Swirling enhances evaporation in several ways:
Swirling generates kinetic energy. It increases molecular collisions and molecular velocities. Molecules break the surface tension and escape into the air (evaporating), where the nose can detect them.
- After swirling, the downward flow on the vessel sidewall forms ‘legs’ or tears. These legs are caused by a surface tension gradient between water and ethanol, disrupting surface tension and promoting evaporation. They tend to separate, a phenomenon known as the Gibbs-Marangoni effect.
- Gravity creates vertical shear on vertical vessel sides, disrupting surface tension and improving evaporation as liquid returns to the liquid pool in the glass.
- Thin wetted layers on vessel walls offer a quick path for rebounding molecules. That path helps break surface tension and boosts evaporation. Conversely, a large liquid pool dampens motion and rarely rebounds to test surface tension.
How Effective Swirling Depends on Glass Shape
Evaporation from thin liquid layers on vessel sidewalls is greater than at the horizontal pooled liquid/air interface. Larger bowl-diameter glasses permit higher swirl velocities. Higher swirl velocities increase the liquid/air interface pressure differential (similar to why water evaporates from a swimming pool much faster on windy days), evaporation layer thickness, and horizontal liquid shear break the surface tension. Larger bowls improve aromas when swirling because of the larger wetted side areas and the higher swirling velocities attainable in larger-diameter bowls. No more myth.
The Swirling Myth Spreads to All Alcohol Beverages:
- The Myth – Swirling is only for wine: All spirits, wine, and beer benefit from swirling. Its benefits extend beyond wine, as experienced beer and spirits tasters swirl to encourage aroma evaporation, especially at low fill levels. Winers encouraged spirits drinkers to swirl. The industry imitates wine drinkers through tacit awareness and unconscious adoption.
- Another Myth – Don’t Swirl Beer: The standard beer pour is close to the rim top, making it hard to swirl. However, the full pour also means there is no headspace. Beer’s effervescence, caused by CO2 or N2, provides sufficient aroma as the bubbles pop. Swirling is not necessary when the glass is full. A glass less full, will release more aromas with slight swirling. Rotating a tilted glass to wet the inside wall also aids in aroma release. When partially consumed more headspace provides swirling or rotating room. Many beer drinkers think wine drinkers are snobs. They reject portrayals of wine drinking, including stems and swirling. Experienced beer drinkers swirl slowly or rotate their glass at lower beer levels in spite of the decrease in effervescence.
- The Most Absurd Myth – Don’t swirl spirits: For decades, the accepted glassware for scotch has been the hard-to-swirl tulip shape. During the scotch resurgence in the ‘60s and ‘70s, ambassadors and educators observed Americans’ intolerance to strong ethanol aromas. This awareness guided their aroma education and tasting guidance. Prohibition (1920-1933) conditioned Americans to adjust their drinks. They mixed soda, fruit juice, and ice with spirits to mask odors. American whiskey drinkers preferred the readily available wide-mouth tumbler, adding water and ice to hide nose-burning ethanol in straight spirits. Scotch ambassadors and educators introduced the tiny-rim tulip-shaped copita, recommended adding only a few drops of water, wafting aromas toward the nose to pre-condition, and warning drinkers not to swirl, all of which will diminish nose burn. Scotch sales skyrocketed. Swirling in large bowl-diameter glassware enhances aromas (see exhibit).
- The Inconsequential Myth – Swirl clockwise in the northern hemisphere, counter-clockwise in the southern: Unnecessary overthinking. Swirling delivers aromas regardless of direction. It’s all about swirling velocities fast enough to break surface tension. Vigorous swirling is better. Right-handed drinkers tend to swirl counterclockwise, and left-handed drinkers tend to swirl clockwise. Do what works best wherever you may be. The Coriolis effect has nothing to do with the effectiveness of swirling. Myth is created by those who have nothing else to do.
Clues to Improving Swirling through Simple Science:
Covering the glass while swirling preserves aromas inside. The technique is cumbersome. Covering will fill the headspace with a higher concentration of aroma molecules until they reach the maximum evaporation possible. This state is called equilibrium. The same number of aroma molecules evaporate as are returned to the liquid, and the vapor cloud in the headspace is fully saturated with aromas. Equilibrium is as good as it gets for displaying aromas, as significantly more aromas are available to smell. Covering during swirling keeps aromas in the glass, ready for detection when uncovered just under the nose. Remove and sniff quickly to get maximum effect.
The Big Cover-up:
In the past, many critics have disdained the use of small glass covers during tastings of expensive spirits as snobbish. Covers provide two advantages: (1) prevent aromas of many different spirits from polluting the atmosphere and confusing evaluators, and (2) provide time for reaching equilibrium before tasting. This is smart, not snobbish. When Arsilica, Inc. began capping tasting samples in 2013, many labeled it snobbish. Today, most professional competitions still cover samples. Serious spirits tasters may use glass caps which must be thoroughly cleaned, or disposable sanitary paper caps of the type commonly used in hotel rooms. Moreover, the glass risk is accidental breakage and ingesting glass shards.
The “Legs” Myth Regarding Nosing and Tasting
“Legs” indicate body and complexity: Nothing could be further from the truth. Legs or tears are mass transfer at the interface between two fluids caused by a surface tension gradient. They are also called the Gibbs-Marangoni effect. Legs are ethanol separating from water when the spirit or wine is draining down the inside wall of the glass, legs or tears do not indicate quality, sweetness, or “body.” Do not confuse the Marangoni effect with viscosity, which is a measurement of pourability or “thickness” of a liquid. The difference, a syrup is viscous; spirits and wine have tears or legs. Surface adhesion, temperature, humidity, barometric pressure, alcohol concentration (ABV), soap residue, cleanliness, glass quality, and the presence of a dishwasher anti-spot coating affect the appearance of legs or tears. Legs contain no useful evaluation information.
The Tongue Map Myth
Tongue Map Lie: The most widely spread myth regarding tasting and nosing is the tongue map, which erroneously ascribes different tastes to different areas of the tongue. Proven wrong since 1974 (see exhibit), a major glassware manufacturer implies validity to the erroneous tongue map to boost sales of wine glasses for each major varietal of grape. Compounding this mistake, many sommelier courses have identified this marketing ploy as science and continue to teach false ideas regarding glassware design effectiveness. Not only is the tongue map myth deceptive, but it is also commonly accepted among many spirits drinkers.
Stay away from seminars that preach that different glassware delivers the beverage to different parts of the tongue, which changes taste. The goal is to influence attendees’ perceptions through suggestion. Consider the physical delivery of a beverage from vessel to mouth; all vessels are placed upon the lower lip, past the lower front teeth when drinking to prevent spilling. Taste is the same regardless of vessel type. Lingual (tongue) contact inside the mouth is not affected by outside-the-mouth vessel shape. Myth busted
Myth – The ISO Spirits Glass:
There is no ISO spirits glass and never has been. Spirits evaluation has evolved through the efforts of a few concerned pioneers who decided to convey their interest and high appreciation of spirits to others, yet they possessed little knowledge of applied science. They intended to bring some semblance of order to tasting, evaluating, and classifying liquors and spirits, and they adopted the historic tiny rim copita “dock glass” as their preferred standard for nosing and tasting. Glassware manufacturers refused to distinguish themselves from competitors by daring to make perhaps unacceptable style changes to a widely accepted shape identity.
In 1977, the ISO (International Standards Organization) adopted a wine glass standard specification, ISO 3591. In a move to improve sales, glassware manufacturers raced to be first to get ISO wine glasses to the public, filling an overreaction to a perceived demand to standardize. As the feeding frenzy for wine glass sales leveled off, glassware marketers quickly discovered the similarity in size and shape of the standard glass to the traditional copita commonly used in spirits tasting. To create the appearance of embracing the science implied by an ISO standard, manufacturers employed creative marketing, taking it upon themselves to label the copita as an ISO Spirits glass (see exhibit).
Over the years, the ISO 3591 has been abandoned by most wine evaluators in favor of larger bowl vessels which provide larger headspace, allowing the nose to be inserted beyond the vessel rim, yet the standard has not been revised. The original copita from the 1700s was designed for 20% ABV fortified wine (sherry) and no doubt contributed heavily to the shape of the standard as established in 1977. Glass manufacturers’ marketing ploy to increase sales, augmented by the public’s wide and unquestioned acceptance of copita and tulips as acceptable spirits tasting, and nosing glasses have created a mistaken impression that has seduced spirits drinkers into believing the copita is the official ISO spirits vessel standard. Myth busted.
Dispelling Myth Improves Evaluation
- One becomes more focused on discovering aroma rather than frivolous, erroneous distractions.
- Exposing the truth raises the educational level and overall quality of tastings and evaluations.
- Reading and embracing science, rationale and logic improve evaluator diagnostic capabilities.
Establishing the Perspective of the Components of Flavor:
Flavor = Aroma (90%) + Taste (5%) + Mouthfeel (5%)
Taste has little effect on the spirit flavor. Pinch or block the nose shut. Taste an equal amount of whiskey, rum, vodka, tequila, gin, and cognac from the same size and style of glass but randomly presented to you while blindfolded so you have no idea which spirit is being sampled. Try to identify each spirit. The burn of 40%+ alcohol on the palate is present in all spirits. Use a diagnostic glass, not a tulip. As a rule, only minor differences in sweetness, sourness, saltiness, bitterness, and umami are apparent in spirits. There are slight differences in mouthfeel, such as oiliness, astringency, and acidity.
From these clues alone, determining the spirit’s source is nearly impossible. The possible sources include grain, fruit, molasses, sugar cane, herbs, or vegetables. This makes the spirit type uncertain (whiskey, cognac, rum, tequila). The blindfold and uniform glassware eliminate visual and touch (feel) clues as to spirit type and blocking the nose leaves only taste and mouthfeel to evaluate. Taste and mouthfeel differences will not accurately identify spirit type or quality, and aromas become the most important factor. Viewing spirits from a different perspective places the contributions of nose, taste, and mouthfeel in a proper order of magnitude and perspective for the serious evaluator.
A New Perspective
Distillers create and market different aromas for drinkers by using different distilling techniques, barrel aging, blending, flavoring, or sources (grains, fruits, sugar cane, etc.), see the exhibit. This perspective, considering the extremely high percentage of ethanol (95%+) in spirit aromas, focuses attention on delivery, identification, and perception of the 90% aroma component of flavor as well as handling the problem of overabundant anesthetic ethanol and its detriment to better evaluation.
The evaluation process is all about getting as many character aromas to the nose as possible to accurately detect and evaluate the 90% aroma component of flavor. Taste (5%) and mouthfeel (5%) can only be improved by sloshing the spirit around inside the oral cavity to ensure that most, if not all sensors have been contacted. Once the human olfactory processes and capabilities, and the basic science of evaporation are understood, the next important step is understanding the contributions and hindrances of glassware and how shape controls aroma detection.
Summary
Sensory science has evolved greatly since the 1960s, in spite of persistent myth. Copita and derivative tulip-shaped glasses were once considered acceptable spirits-tasting glasses. Improved methodology and applied statistics have improved sensory evaluation to achieve a 95% confidence level, much to the satisfaction of those few food and beverage industry companies that utilize professional sensory service companies or create their departments.
Therefore, serious evaluators must begin to determine and rely on facts over repeating disproven myth and erroneous information to be accepted as qualified critics. See the sensory science approach to choosing the best glass.
State-of-the-art sensory science can evaluate and compare glassware. It reliably determines differences in aroma profiles attributable to glassware size and shape. Evaluators and the spirits industry must rely on science to replace myth with truth and pave the way for better understanding, raising the quality bar, and determining consumer preferences and predictability. See how we designed the best spirits glass.
