Parchment paper, baking paper, liners or bakery release paper is cellulose-based paper that has been treated or coated to make it non-stick. It is used in baking as a disposable non-stick surface. It should not be confused with wax paper or waxed paper, which is paper that has been coated in wax.
Modern parchment paper is made by running sheets of paper pulp through a bath of sulfuric acid (a method similar to the way tracing paper is made) or sometimes zinc chloride. This process partially dissolves or gelatinizes the paper. This treatment forms a sulfurized cross-linked material, with high density, stability, and heat resistance, as well as low surface energy — thereby imparting good non-stick or release properties. The treated paper has an appearance similar to that of parchment and, because of its strength, is sometimes used in legal documents for which parchment was traditionally used. (However, parchment paper is manufactured with acid, and has a low pH, making it inappropriate for archival documents where acid-free paper is the better choice.)