August 16, 2021 3 min read
A glass for tasting and drinking.
The tasting glass has sacrificed the folklore of the silver metal cup or 'tastevin' in order to benefit from rigour, objectivity and repetitiveness in the organoleptic evaluation of wine. The glass enables all wines to be compared under the same tasting conditions. Today, it is used by most wine professionals when conducting official tastings in all wine-producing regions of the world. Whatever the place of tasting, it enables the method to be reproduced and observations to be compared objectively. It is an effective working tool that can be used on the wine enthusiast's table.
If you are a true enthusiast, leave aside the glassware on your wedding list and buy some official tasting glasses from INAO, Institut national de l'origine et de la qualité, or defined by the UNI ISO 3591 standard, the cost of which is not prohibitive, and always do your tastings with these glasses.
The arches that appear on the wall of a glass have nothing to do with the glycerine content of the wine. This phenomenon can also be observed in a glass containing good-flavoured alcohol, grappa or brandy, which do not contain glycerine.
BOILING POINTS (AT SEA LEVEL):
The interpretation of these three boiling points is very simple: alcohol evaporates (passes into a vapour state) more easily than water and much more easily than glycerine.COMPOSITION OF THE WINE, DEPENDING ON THE TYPE OF WINE:
By swirling the wine on the wall of the glass, its surface tension causes an invisible film of alcoholic liquid to adhere to the entire wet surface. The alcohol, which has a very low boiling point, evaporates from this film, the higher the temperature of the glass wall. It is this evaporation flow that carries the aromas.
The maximum evaporation of alcohol occurs at the upper limit of the liquid film, what is called the meniscus where the three phases coexist.
The solid phase: the glass, the liquid phase: the film, the aeriform phase: the air and the evaporated alcohol.
At this meniscus of density 0.990, the lighter fraction of wine evaporates (0.780) and the density of the mixture increases (0.991 to 0.995) approaching that of pure water (1.000).
This mixture accumulates in a ring of increasingly heavy upper level, which forms a crown inside the glass. The surface tension no longer supports this excessively heavy ring: the mixture drops onto the wall of the beaker at certain points giving the impression of tears slowly falling over the film.
Nature has a horror of vacuums, the evaporated part of the alcohol is replaced by alcohol that rises in the middle of the tears, forming pillars, feeding the system, as if it were an 'alcohol pump'.
This phenomenon has been known for more than a hundred years and was explained by the British physicist James Thomson. It is also known under the name of the Marangoni effect, an Italian who invented a water pump using the same principle.
There is therefore no relationship, or indication, between the intensity of the phenomenon and the glycerine content of the wine.
The temperature of the environment and the alcohol content of the wine influence the intensity of the 'alcohol pump'. Maximum results are achieved with a high wine grade and in a very warm room.
Attention! These two apparently simple steps interfere with the observation of the arches.
The surface tension, which holds the wine film, depends on the state of the surface of the wall of the glass (its crystallographic state). The way your glass has been washed, rinsed and then dried interferes in the observation of the phenomenon: detergent, rinse aid and limescale remover produce deposits on the surface which modify the reactions of the film on the wall.
We should also remember that the way in which the flute is washed and rinsed (a champagne glass made of glass, not plastic!) also influences the release of champagne bubbles.
Giuseppe Meglioli “The Taster”
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