Recently, it has been found that surface tension of a colloid solution maintained lower value by microwave irradiation even after the microwave was turned off. The results verified bubbles around particles due to microwave. In this study, the surface tension and particle-bubble were monitored during and after the irradiation for suspension from an aqueous solution of ferric chloride. The surface tension decreased with temperature during the irradiation. Furthermore, the tension did not recover to the original value. Simultaneously, it was confirmed that nano-bubble was formed around the particle when nanoparticles are formed during microwave heating. The effect of an anti-solvent, ethylene glycol, on the process was also investigated. It was found that ethylene glycol affects the bubble growth significantly during microwave irradiation. In contrast, the particle size was slightly affected by ethylene glycol. The results can be explained in terms of the H-bond networks of molecules around the liquid–air interface.