The benefits to the formulator of wine, whisky and coffee are well known – coffee to help waken the formulator at the start of the day and wine or whisky to celebrate or commiserate over the day’s results. However, the tears of wine and the coffee stain effect (Figure 1) are well known examples of the Marangoni effect,1 an important physical phenomenon also seen in paints and coatings that is often related to similar phenomena, often with undesirable consequences. Both are examples of liquid flow induced by surface tension forces.
FIGURE 1 » Wine tears, coffee stain and whisky patterns on glass.