Influence of Evaporation on Soap Film Rupture

Abstract

Although soap films are prone to evaporate due to their large surface to volume ratio, the effect of evaporation on macroscopic film features has often been disregarded in the literature. In this work, we experimentally investigate the influence of environmental humidity on soap film stability. An original experiment allows to measure both the maximum length of a film pulled at constant velocity and its thinning dynamics in a controlled atmosphere for various values of the relative humidity [Formula: see text]. At first order, the environmental humidity seems to have almost no impact on most of the film thinning dynamics. However, we find that the film length at rupture increases continuously with [Formula: see text]. To rationalize our observations, we propose that film bursting occurs when the thinning due to evaporation becomes comparable to the thinning due to liquid drainage. This rupture criterion turns out to be in reasonable agreement with an estimation of the evaporation rate in our experiment.

Stability of big surface bubbles: impact of evaporation and bubble size

“…To provide more insight into these systems, the thickness evolution of film at the apex of the bubbles was measured using a reflectometric technique, described in more details in [18,21]. These experiments were conducted in a closed chamber which humidity was controlled with another device described in [31].…”

“…In the following, the goal is to extract the bubbles lifetime. We will make use of a hypothesis similar to Champougny et al [21] (in the case of vertical flat films in continuous generation) and Poulain et al [9] namely that what sets the lifetime of surfactant-stabilized films is the balance of capillary/gravitational thinning on one side and the evaporative thinning on the other side. We will therefore proceed as follows: we first look for the thickness h c for which, given a bubble size and an evaporation flux, the thinning due to drainage (two first terms at the right hand side of Equation 10) equals the thinning due to evaporation.…”

“…Lhuissier et al proposed a drainage model that will be discussed further, based on the coupling between a capillary driven flow localised at the foot of the bubble and the periodic emission of so called marginal regeneration plumes, as first reported by Mysels et al [19] Another potential contributor to thinning is evaporation, about which literature is much more scarce with only one recent paper to address its impact on the stability of surface bubbles [9]. However, the few systematic studies of the stability of thin films under controlled partial pressure of water in the gas phase, relative to the saturation pressure (ie relative humidity) report a strong impact of this parameter [20,21,22]. Bubble artists also invariably report decreasing stability of their films with decreasing humidity.…”

The Life of a Surface Bubble

“…Going one step further, Champougny et al [55] measured the thickness evolution of planar thin films during the continuous extraction of a frame from a soapy solution in a humidity controlled environment. The data are presented in Figure 6b.…”

“…Cross symbols represent repeat of experiments. (b) Extracted with authorization from Champougny et al[55]. Thickness evolution 1 mm below the superior frontier of a thin film extracted at 0.5 mm s −1 from a 5 cmc TTAB solution.…”