The pH value of the cold extract can be determined according to ISO 6588-1 or DIN 53124.

Extract 2.0 g of air-dried sample in deionised water in a closed Erlenmeyer flask for one hour at 20°C to 25°C. The extract is then transferred via a glass frit into another glass flask. The extract is then transferred via a glass frit into another glass flask, mixed with 2 ml of a 1 M KCl solution according to ISO 6588-1 and the pH is measured.

The measurement of pH and conductivity is a quick and simple method for characterising the inorganic contaminant load. In addition, the pH value is determined e.g. in connection with ageing resistance or the effectiveness of quantity processes for paper deacidification.