Description

TAPPI T 428 – Hot Water Extractable Acidity or Alkalinity of Paper

This method, based on the work of Kohler and Hall (1), measures the titratable acidity or alkalinity (end point at pH 7.0) of an aqueous extract of paper (filtered and extracted by boiling water for 1 h). It specifies one extraction and so does not measure the total acidity or alkalinity of paper, for which exhaustive extraction is required.

It may be applied to writing, printing, and sized industrial paper but is not intended for testing electrical insulating papers.

NOTE 1: This method measures the pH of the bulk extract as prepared in the method, and as such, measures the combined acidity and alkalinity of the base paper and any added fillers or coating materials.