This part of ISO 9184 specifies the preparation, use and colour reactions of Graff “C?? stain in fibre furnish analysis. It should be used in conjunction with ISO 9184-1 and, if necessary, with other staining tests defined in ISO 9184-2.
The field of application of Graff “C?? stain is very large; it allows the identification of almost all the common papermaking fibres. However, this is based upon very minute differences in the shade and strength of the colours, and accordingly calls for a great deal of training and experience. In practice, the main applications of the Graff “C?? stain are as follows:
- Differentiation of chemical, semi-chemical and mechanical pulps.
- Differentiation of bleached kraft and sulfite in softwood pulps. Generally, the colour difference is sufficient for counting the fibres.
- Differentiation of kraft and sulfite in hardwood pulps. The difference in colour is more obvious in unbleached than in bleached pulps.
- Differentiation of softwood and hardwood pulps (except dissolving grade pulps). In kraft pulps, the colour difference is sufficient; in sulfite pulps it is somewhat weaker, although in most cases sufficient for counting.
- Differentiation of bleached straw and esparto pulps in softwood pulps. The colour difference is distinct.