This non-destructive test may be used to measure the hydrogen ion concentration (pH) on the surface of the paper in books and documents that constitute the collections of libraries and government archives. This method serves as an alternative to T 509 Hydrogen Ion Concentration (pH) of Paper ExtractsCold Extraction Method, because it avoids the destruction of printed material in the determination of the permanence expected for paper (see also 11.2). pH values obtained through the application of this method to sized materials such as writing, printing, and industrial papers reflect only the pH of the surface of these materials and should not be construed as pH values which may be determined by the cold water extraction method of the same material (1).