Printing techniques apply a thickened dye or ink paste through a screen embossed with a pattern onto a fabric. Modern systems include flatbed screen, rotary screen, and engraved copper roller printing. Digital inkjet printing applies the ink as drops controlled by a CAD system; no screen or engraved pattern is used. Printing is further classified as either dyestuff printing or pigment printing.
Preparation of the Print Paste
The specifics of print paste formulation depend on the fiber content, the dyestuff, and the printing machine used. Typical ingredients include dyes or pigments, thickeners, sequestering agents, surfactants, humectants, defoamers, catalysts, and other auxiliaries.
Printing of the Fabric
Fabrics can be printed effectively by several methods, including rotary screen, flatbed screen, engraved roller, digital inkjet, and transfer printing.
Drying of the Printed Fabric
After the ink paste has been printed, the fabric has to be dried and either cured or steamed to react the paste. For continuous drying, a tenter frame, a conveyor-belt dryer, or a loop dryer is used.
Fixation of the Printed Fabric
Depending on the layout of the printing plant, the printed fabric may go through the fixation process immediately after drying or be held for later fixation. The colorant type and production issues dictate the choice of fixation method. Methods include atmospheric steaming, pressure steaming, and dry heat.
In dyestuff printing, fixation of the printed fabric is followed by thorough washing and drying. This step is necessary to remove unfixed dyestuff, thickener, alkali, and other components of the print paste. Fabrics printed with pigment are not always afterwashed. Whether they are afterwashed or not depends on the pattern and the shade.