Fingering This figure on the left depicts the beginning of a finger. The red arrows indicate dissolution of the alcohol into the water. Region A has less alcohol per unit volume relative to B so the surface tension gradient is larger. This results in the continued movement of the protrusion outward, toward the region of higher surface tension, resulting in a finger. This picture on the left shows a very skinny and sharply pointed Marangoni driven protrusion, which we will call a finger. Surface tension gradient driven fingers such as this occur under particular conditions that vary between the different alcohols. This picture on the right shows what happens when a finger protrudes far enough to overcome the molecular forces holding the drop together. When this occurs the finger “necks down”, gets smaller where it is attached to the drop, and, within an average time period of one tenth of a second, separates to become its own drop.