Method for processing an article by contacting the article with a dense fluid. The article is introduced into a sealable processing chamber and the processing chamber is sealed. A dense fluid is prepared by introducing a subcritical fluid into a pressurization vessel and isolating the vessel, and then heating the subcritical fluid at essentially constant volume and essentially constant density to yield a dense fluid. At least a portion of the dense fluid is transferred from the pressurization vessel to the processing chamber, wherein the transfer of the dense fluid is driven by the difference between the pressure in the pressurization vessel and the pressure in the processing chamber, thereby pressurizing the processing chamber with transferred dense fluid. The article is contacted with the transferred dense fluid to yield a spent dense fluid and a treated article, and the spent dense fluid is separated from the treated article.