A method and apparatus for cleaning a stack of secure instruments is disclosed. Each secure instrument includes a substrate, visual data and a security feature. The method and apparatus include exposing the stack to a supercritical fluid at a temperature and a pressure and for a duration sufficient to clean each secure instrument and not compromise each security feature and each visual data, and maintaining a securing mechanism on the stack during exposure of the stack to the supercritical fluid such that cleaning each secure instrument includes one or more substances from each secure instrument into the supercritical fluid.
