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TAPPI T 244 Acid-insoluble ash






Acid-insoluble ash in wood, pulp, paper, and paperboard

Scope and Summary

TAPPI T 244 Acid-insoluble ash describes a procedure for determining the acid-insoluble ash content of cellulose samples. The sample is dry-ashed and the residue treated with hydrochloric acid. The insoluble residue is filtered, washed, ignited, and weighed. This method measures all acid insoluble material.


Silica or silicates, the major components of the acid-insoluble ash, are normally present in wood and pulp in very small quantities. If excessive amounts are present and carried into the finished paper, particularly of “fine” or specialty grades, they may cause undesirable abrasion of metal repeatedly applied to the paper, such as punches, dies, knives, or type. Paper and paperboard may be filled or coated with clay (alumino-silicates) making the acid-insoluble ash content considerably higher.


This test is performed in duplicate. At least 55 grams and preferably 120 grams of dried material should be submitted per sample. A minimum of two samples submitted at the same time is required. IPS uses porcelain crucibles to ash samples in place of platinum dishes.

Please note:

SGS-IPS cannot sell or otherwise provide standards, specifications, or test procedures to third parties.