How a smell travels from your wine to your nose

At a restaurant, the sommelier pours, stops a third of the way up the glass, and walks off with the bottle. You might suspect stinginess. The British critic Jancis Robinson admits the gesture "may appear mean or stingy," and still advises filling a glass preferably less than half full. The empty part of the glass is working for your nose.

A wine's smell makes a short journey before it reaches you. It leaves the wine through its surface, rises through the air trapped in the glass, then exits through the opening, and at every stage the shape of the glass changes something. Professionals take this seriously enough that international competitions held under the patronage of the International Organisation of Vine and Wine serve every wine in, at the very least, a standardized glass.

Departure: the surface

In the mid-1960s, Jules Chauvet, a wine merchant and chemist in Beaujolais, poured the same red wine into a Petri dish, a wide-necked bottle and a balloon glass. The three did not give off the same aromas. He drew a simple idea from it: what a wine smells like depends on how much of its surface touches the air, and on the ratio between that surface and the volume of the container.

Jancis Robinson turns this into very practical advice: fill the glass up to its widest point, where the wine offers the most surface to the air. In most wine glasses, that point sits fairly low, which brings us right back to the sommelier.

The climb: the chimney

At the University of Reims, Gérard Liger-Belair and his team used a laser to map the alcohol vapor hovering above champagne served in the standard tasting glass, filled halfway. The vapor is densest just above the liquid and thins out as it rises: three centimeters (just over an inch) higher, there is a third as much.

The measurement was made on champagne, but it helps explain why a glass filled to the brim doesn't smell like one filled a third of the way. A full glass would put your nose right next to the most alcohol-laden layer, and Liger-Belair and his colleagues point out that a strong dose of alcohol vapor makes the nose tingle, or even burn. A glass filled a third of the way would give the alcohol a few centimeters (an inch or so) to thin out. The Reims researchers even suspect that less alcohol in the air at nose level lets the fruit come through better. Nobody has measured that yet.

Arrival: the opening

In Tokyo, Kohji Mitsubayashi and his colleagues photographed the alcohol escaping from a glass. Their device is a mesh soaked in enzymes that glows when it meets alcohol vapor, filmed by an ultra-sensitive camera. Above a wine glass holding a cool wine, the image shows a bright ring along the rim and a darker center, with less alcohol. Above a straight glass or a cocktail glass: no ring.

For Mitsubayashi, the ring lets you enjoy the wine's aromas without the alcohol getting in the way. That is also what the international standard for tasting glasses is after, with an opening narrower than the bowl to better concentrate the smells. And the center of the glass happens to be exactly where you put your nose without thinking about it.

And the aromas?

One question remains: if the glass arranges the alcohol so neatly, does it also change the aromas themselves? At the University of California, Davis, Greg Hirson and two colleagues set out to check. They poured a Gewürztraminer into five glasses, including the standard tasting glass and a plain laboratory Erlenmeyer flask, analyzed the air above the wine, and had a panel of tasters smell each glass. Right after pouring: almost no difference. A few minutes later, the standard glass and a Bordeaux glass brought out more of the fruit, while a red wine glass played up the hot sensation of alcohol.

So shape really does act on the nose, especially once the wine has had time to settle, and the small, inexpensive standard tasting glass holds up very well. Interviewed later by SevenFifty Daily, an American trade publication for wine professionals, Hirson confirmed that the effect of the glass is detectable, then put it in its place: "Atmospheric pressure, mood, health, company, lighting, sound, wineglass shape, temperature, focus, and an infinity of other factors will change how the wine is perceived." Glass shape made his list, wedged between sound and temperature. He had set out to see whether there was a scientific basis for having the "correct" wineglass for each wine. "I don't think there is," he said.

Jancis Robinson, who designed her own glass, grants that a glass matched to a particular wine is "usually a small percentage better." But, she said, "life is just too short" to own lots of nearly identical glasses. And you: what's your glass like?