Sulphite‐based resist styles for digital printing cotton fabrics

Discharge printing provides a method of producing either a white or coloured image on a solid ground fabric; unfortunately, the shade range from this process is limited. An alternative approach to discharge printing is resist printing, which provides prints that are almost indistinguishable from those achieved by the discharge printing process and has the advantage of offering a wider shade range. In resist printing, the resist agent prevents fixation of the background colour by chemical (resist agent inhibits dye fixation) or physical (resist agent inhibits dye absorption) processes and so yields a white print. Printing is carried out on grounds that have been pad‐dry ‘dyed’ with selected reactive dyes; the dyes must not fix during this process otherwise white grounds are not achievable – subsequently fixation is achieved by steaming after digitally printing the resist agent. In this paper, the resist agent studied is sodium sulphite, which selectively blocks reactive groups in reactive dyes – the ground shade reactive dye must be deactivated in this reaction to produce the resist effect. A coloured print may be achieved by incorporating a suitable reactive dye, of a different class to that used in the ground shade, which is not deactivated by the resist agent, in the resist ink.