Process for heat treating textile substrates to give a colored pattern

A single, uniform application of dye is employed to generate a pattern dyed substrate wherein the pattern and pattern-complementary areas are dyed by the same dye, but at different levels of fixation. Dye is uniformly applied to the substrate, and optionally dried, without fixation. Heat is applied to the substrate uniformly as well as selectively in a pattern configuration. The uniform heating serves to fix the dye in the pattern-complementary areas at a pre-determined level. Selective heating in pattern areas serves to fix the dye at a higher level of concentration in pattern areas than is found in the pattern-complementary areas, resulting in a multi-tone effect. Optionally, the heating in pattern areas may be sufficient to cause shrinkage or other thermally-induced physical modification to the substrate, in perfect registry with the pattern-dyed areas.