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 TAPPI T 509 “Hydrogen Ion Concentration (pH) of Paper Extracts - Cold Extraction Method,” and TAPPI T 435 “Hydrogen Ion Concentration (pH) of Paper Extracts - Hot Extraction Method,” because it avoids the destruction of printed material in the determination of the permanence expected for paper. 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.  pH determinations by the different methods are not comparable. Fillers and coatings, particularly those containing carbonate, can have an effect on pH.

 

Because the useful life of most papers is primarily a function of the acidity of the paper, it is necessary that the concentration of the hydrogen ion in the paper be known so that appropriate preservation and/or restoration techniques may be employed to extend the useful life of books and documents which are determined to be acidic.

 

This test is performed in duplicate. At least 5 sheets of paper should be submitted for each sample. Gloves should be worn when handling the papers. Do not include any papers touched with the fingers.