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: a) Differentiation of chemical, semi-chemical and mechanical pulps. b) Differentiation of bleached kraft and sulfite in softwood pulps. Generally, the colour difference is sufficient for counting the fibres. c) Differentiation of kraft and sulfite in hardwood pulps. The difference in colour is more obvious in unbleached than in bleached pulps. d) 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. e) Differentiation of bleached straw and esparto pulps in softwood pulps. The colour difference is distinct.