Abstract: A preservation device allows for the safe storage of wine and other liquids subject to change over time. When wine is stored in a partially filled container, the wine degrades due to the presence of oxygen. The preservation device has an integral inelastic low mass barrier bag that fits within the wine bottle, in an unexpanded or collapsed form. The barrier can be expanded into the headspace of the container by introducing air into the bag from a pump, excluding ambient gasses and reducing the amount of air in contact with the stored fluid. Because of its low mass, the inelastic barrier bag remains substantially expanded in the container due to the surface attraction with the container walls as well as the rigidity imparted to the barrier bag by its material characteristics. No stopper is required to maintain the barrier in an expanded state.