Abstract: An ink composition is provided which is suitable for use on bare metal, for example, tinplate or aluminum as well as on such metals having organic coatings applied to surfaces thereof. The compositions may also be used on plastic containers or retortable pouches comprising plastic or plastic-metal foil laminates. The inks are suitable for use in contact printers or in jet ink printing techniques. The ink compositions are thermotropic, i.e. they change color in the presence of steam at elevated temperature and are useful as sterilization indicators. The inks comprise essentially a binder resin component, an alcohol solvent and a colorant which reacts in the presence of steam at elevated temperature to produce a visible and permanent color change.