Textile printing is a process through which a pattern, color, or combination thereof is applied to the surface of a textile. When a fabric is dyed, all the fibers absorb the dye and assume the designated color. With textile printing, however, only the surface fibers or specified area of the textile receives the color or pattern. As a result, the color is not applied uniformly but in selected regions. Textile printing enables textile manufactures to achieve various aesthetics, from complex geometric patterns to more simple designs.
There are several common methods associated with modern textile printing, including flat-bed screen printing, rotary screen printing and heat transfer printing. Other methods, such as roller printing, stencil printing, and engraved copperplate printing, may also be appropriate for specific applications.
Flat-Bed Printing
Flat-bed printing, an automatic or semi-automatic process, is the preferred process when transferring precise images onto the surface of a textile, typically polyester or related fabric. To transfer the image to the fabric, a metal frame is used to hold the textile fabric. A corresponding screen is then coated with a light-sensitive emulsion and the predetermined design is transferred onto this screen, via photomechanical techniques. This process allows the textile to receive color in appropriate areas without coating the entire textile. Flat-bed printing methods can vary, but mainly differ in terms of screen mobility. In continuous methods, for example, the screen moves and the textile is stationary; in non-continuous methods, the textile moves and the screen remains stationary.
Rotary Printing
Rotary printing is similar to flat-bed printing, except that it is a completely continuous process. Nickel cylinders are used to roll the flat screens (hence the term rotary) onto the textile. Parts of each cylinder are prepared to transfer the printed image using photomechanical methods. As a result of the introduction of the cylinder, printing speed is increased. Up to twenty-four colors can be printed using rotary printing, and the method can also be used for printing images on paper. The process is fast, enabling patterns to be changed rapidly or printed continuously.
Transfer Printing
Transfer printing typically involves either sublimation transfer, melt transfer, or film transfer. Sublimation involves the transfer of a design using a dry heat. Dyes, typically disperse dyes, are prepared on a paper film, which is then heated as it is placed onto the textile surface. As the paper heats, the dye is transferred to the fabric—the dye “sublimes,” from the vaporous stage it assumes upon heating, into a solid state as it makes contact with the fabric. Melt transfer typically transfers dye to a textile through the melting. A wax-based ink is usually printed on paper; an iron is then used to apply paper to the fabric, thus transferring the ink to the textile. In film transfer printing, a design is transferred as a film from paper, using heat and pressure to adhere the ink to the textile. Transfer printing can produce high quality prints and is especially useful for short-production runs. Additionally, there are very few byproducts and pollutants released during the process. However, transfer printing is a slow process for high-production runs and the method tends to be limited to polyester textiles.