BURSTING OF SOAP FILMS .I. AN EXPERIMENTAL STUDY

The bursting of plane vertical soap films has been studied by means of photographs taken in the light of a submicrosecond flash at a predetermined interval after initiation by a perforating spark. Each such photograph gives a detailed picture of the over-all instantaneous state of the bursting film. A timed series of photographs gives the velocities involved. The effects of film thickness, bulk viscosity, and surface structure have been explored. Contrary to the premise of previous theories an aureole of thickened film has been found to spread ahead of the narrow rim surrounding the growing hole. Nevertheless, typical thick mobile films have rim velocities close to those required by conservation of momentum in the absence of an aureole. Thin mobile films and rigid films show markedly lower speeds. The periphery of the holes is quite smooth except for the thinnest second-black" films which have a scalloped rim with inward protrusions and drops. The potential of these observations for the study of high-speed surface and bulk kinetics is indicated and several problems encountered in these experiments and in their interpretations are discussed."