Spontaneous Draining of Liquids from Vertically Oriented Tubes

This paper describes experiments where liquid-filled tubes, with the bottom ends open, were pulled vertically from a reservoir. If the open diameter on the bottom of the tubes was sufficiently small, liquid was retained. Otherwise, if sufficiently large, the tubes drained from the bottom up. The critical diameter of the opening at the bottom of the tubes ranged from 10-15 mm for water to >5 mm for a dense, low surface tension, perfluoroether oil. The ability of relatively large diameter tubes to retain liquid is attributed to a combination of materials properties and atmospheric pressure. If surface tension were acting alone, the tubes would have had to be much smaller to prevent drainage or spillage.