The present invention relates to methods and systems for densifying liquids, specifically the densification of cryogenic propellants. 2,9-dichloroquinacridone is added to the milling composition of the crude gamma or crude beta quinacridone. The rear end of each of the running boards is attached to a fender. is supplied to a contaminated object to oxidize and dissolve a chromium oxide film by an oxidizing dissolving process.