Description

This method applies to an extract of the whole paper or board. Surface-treated papers or boards may yield quite different pH for an extract of the surface layer from that of the whole paper or board.

The determination of the pH value of distilled water extracts of paper is a test commonly used by paper manufacturers and paper users, when a knowledge of the degree of acidity or alkalinity of the paper is considered desirable for assessing whether the paper will be satisfactory for a particular purpose. Papers requiring a high degree of permanence, or intended for hygienic purposes, or for the wrapping of foods and metals are examples of papers that may be subjected to this test.

This standard prescribes a cold water extraction of paper. AS/NZS 1301.422s prescribes hot extraction, but, as this does not necessarily give the same results, it should be regarded as a different method. The difference is due to heat-induced hydrolysis of materials in the paper. The choice of method is determined by the use to which the results are to be put, and the references listed in annex A should be consulted.

This method conforms to the relevant cold extraction sections of ISO 6588:1981, Paper, board and pulps – Determination of pH of aqueous extracts.