These are monochlorotriazine reactive dyes having a low reactivity and low substantivity. Since these dyes have low reactivity, they require more severe conditions for fixation with cellulosic materials. They are readily soluble by pouring water of 80-85șC on powder & stirring well. They are applicable on cellulosic materials by both dyeing as well as printing methods.
In comparison with cold brand dyes, the `H' brand dyes require either a long steaming time or a high thermo fixation temperature (with urea) for optimum fixation. H dyes of low to medium substantivity and medium to high reactivity are most suitable, dyes of very low substantibity may lead to migration problems in dyeing prior to fixation.
When low concentration of highly substantive dyes are used, tailing becomes evident. Tailing is avoided by selecting dyes of low or medium substantivity, using small padding troughs fed to constant level and operating at the highest running speed commensurate with the needs of the rest of the process.