The same results were also observed during the third irradiation/dark cycle, leading to a global decrease of the surface tension, of more than 3 mN/m after three irradiations, while the global decrease amounts to only 2 mN/m in the dark. An attempt to reverse the effects of the photoisomerization was performed under 300 nm irradiation, without success, probably due to the slow expulsion of the Z-isomer.