The standard describes the determination of the residue (ash) after incineration at 525 ° C of paper, cardboard and pastes. It is applicable to all types of paper, cardboard and pulp samples. The ash can be composed of:
a) mineral substances in the pulp and various residues of the chemicals used in its manufacture,
b) metallic substances from the pipeline and machinery, and
c) fillers, pigments, patinas or residues from various additives.
In samples containing calcium carbonate there is practically no carbonate decomposition with incineration at 525 ° C. Other fillers and pigments such as kaolin and titanium dioxide also do not undergo changes in incineration at 525 ° C. Consequently, the residue of incineration as determined by the standard provides a good estimate of the total inorganic substance present in the sample, provided that the sample does not contain other minerals that decompose at this temperature or at a lower temperature. For example, magnesium carbonate and calcium sulphate can, at least in part, decompose at temperatures below 525 ° C.