The 'arc in water' reaction system which can produce carbon nanotubes and related materials was investigated using a unique condition with microgravity environment. From such condition, we can gain some information about gas emersion from the gas-liquid interface and expansion rate of gas bubble at the arc zone without condensation of water vapor. Based on the results obtained from microgravity condition together with normal gravity condition and the use of carbon-contained liquid to host the arc plasma, we modified the previous model of the relevant reaction field. Conclusively, we found that gas film is generated in the gas phase at the gas-liquid interface, and this film may block the carbon vapor to arrive the liquid phase. From this phenomenon, the products expected from direct reaction of carbon vapor with liquid components may be hardly produced. (C) 2007 Elsevier B.V. All rights reserved.