One–pass pigment printing of bright colours on a dark textile background

When printing a coloured pattern over a dark textile background, the latter shows through, since the coloured pigment and the binder are transparent. An opacifier (titanium dioxide) can be added to hide the dark ground, but this reduces the brightness of the pigment, so that red becomes pink. An opacifier has been found, diatomaceous earth (diatomite), which has good hiding power for the dark ground, although not reducing the colour strength of a coloured pigment mixed with it, allowing the printing of bright colours. The colour strength of a red–pigmented printing paste opacified with titanium dioxide increases slowly and linearly with pigment concentration. In contrast, when printing the red paste without opacifier on a white background, colour strength increases rapidly and then levels off at 3–4% pigment concentration. A diatomite opacified paste behaves similarly, that is, like a coloured, transparent medium applied to a white ground.