A method for sealing a container having an opening by contacting the opening with a mixture including a phenethylamine and a first polymer, adding a fluid to be contained to the container, and then adding a second mixture, comprising a second polymer, whereupon an interaction between the first and second polymer mixtures result in a seal being formed over the opening, thereby containing the fluid. The first polymer is typically a water-swellable polymer and the second polymer is typically a hydrophilic polymer that will form an interpenetrating network with the swellable polymer.