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In the new suggested process, the garments or fabrics are placed in a washer-extractor which is similar'to the type that would have been utilized in a conventional desizing operation utilizing an enzyme. The washer-extractor is then filled with water having an elevated temperature, that is, about 120 to 185°F. The higher the temperature the greater the discoloration. It is understood that at the higher temperatures the reducing agent selected must have a requiste temperature stability. The pH of the bath is adjusted according to the type of reducing agent utilized. The reducing agent is then added to the bath. The bath is normally agitated for about 0.3 to 1.0 hours and then the water is extracted and the garments or fabrics are rinsed with water. The garments or fabrics can then be further processed if desired.
The amount of reducing agent utilized is determined by the type of reducing agent utilized and the effect desired. For example, in a commercial size washer-extractor in which about 180 denim jeans are to be desized, when thiourea dioxide is the reducing agent, about 0.75 lbs is used in a bath containing 260 gal. of water to achieve a light blue effect. While 1.5 lbs gives a pale blue effect. With sodium hydrosulfite as the reducing agent, about 1.75 lbs is utilized to achieve a similar result. It is understood that compounds such as polyvinylpyrolidone can be added to the system to prevent redeposition of the dye removed from the garments during reduction.
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