Term (also legs, legs, windows, tears) for the liquid structures on the inner wall of a wine glass, which (can) form when the glass is pivoted in a circular motion. The swiveling creates a more or less high, vertically arranged liquid film (wine). At the top edge, the film begins to thicken and contract into viscous, tear-like drops. These then flow back down to the liquid level. The mixture of water and water is decisive for the phenomenon of wine alcohol, would also work with any other mixture of two liquids with different boiling points. It would therefore not occur with pure water or pure alcohol alone. In the right picture the tears or stained glass windows can be seen in the shadow (see arrow).
Liquids are held together by the attraction of their molecules, the so-called adhesion. The type of alcohol ethanol at 78 ° C has a significantly lower boiling point than water. If parts of the alcohol evaporate, the surface tension of the film is changed, the remaining liquid contracts and flows down in the form of more or less large drops. The falling drops form windows. Depending on whether the distances between these tears are narrow or wide, the alcohol content getting closed. The smaller the distance between the tears (in the "pointed arch style"), the more viscous (thicker) is the wine and higher the alcohol content. The further the distances are (in the "arch style"), the lower the proportion.
The effect occurs increasingly from an alcohol content of at least 12% vol. Sometimes it is claimed that the stained-glass windows also have a high salary glycerin Clues. However, this is not correct because glycerin has a significantly higher boiling point than water at 290 ° C. It is almost exclusively the alcohol content that is decisive. There are alcohol content meters that use this effect. These consist of a glass capillary with a funnel and a measuring scale. A little wine is poured in at the top and flows out again at the bottom. Due to the adhesion, some wine remains in the capillary that does not flow out. The alcohol content can then be determined from the height and temperature using the table. The procedure is accurate to 0.5%.
Already in 1855 the British physicist James Thomson aka Lord Kelvin (1824-1907) recognized this phenomenon, which he called "tears of a strong wine". The discovery is often wrongly attributed to the Italian physicist Matteo Marangoni (1840-1925), who published it in 1871 and is therefore also called Marangoni convection. See also under wine address. wine review and Weingenuss,