(720j) Tears of Wine: New Insight on an Old Phenomenon

Anyone who has enjoyed a glass of wine has undoubtedly noticed the regular pattern of liquid beads that fall along the inside of the glass commonly referred as ‘tears of wine.’ The fascinating feature of this phenomenon is that the tearing continues to take place even if the liquid within the glass is stationary, which is possible only if there is a flow against gravity in the liquid film on the inside of the glass. In 1855, J. Thomson identified the driving force for the upwards flow necessary for the continuous formation of tears as a gradient in interfacial tension. Some 15 years after Thomson, Marangoni  described this phenomenon, which is commonly associated with his name. There has been considerable interest in understanding both the Marangoni flow within the liquid film and the instability leading to the formation of tears. It is generally accepted that the flow leading to wine tears is due to a composition gradient that results from the evaporation of ethanol, which in turn produces an interfacial tension gradient. Here, we revisit the tears of wine phenomenon using a simple hydrodynamic model and a novel experimental technique. Our results demonstrate that the Marangoni force responsible for wine tears is the result of both composition and temperature gradients whose relative contribution depends on the bulk ethanol concentration. The methods developed here can be used to obtain a deeper understanding of Marangoni flows induced by evaporation, which are ubiquitous in nature and modern technologies.