Discharge means removal and the discharging system means the process which can produce a white or colored effect on a previously dyed ground. Discharge styles have been important since the earliest days of textile printing. This discharging of color from the previously dyed ground is carried out by a discharging agent which is actually an oxidizing and reducing agent capable of destroying color by oxidation and reduction. Discharge prints can be made with rollers and screen methods. They are not widely used because production costs are high. Flow Chart of Discharge Printing Process is followed:
Flow Chart of Discharge Printing Process:
Discharge printing is done in the following way.
Fabric plaited on the table
Apply printing paste with the help of screen
Curing at 190 ºc (belt speed 3m /min)
Discharge printing popular as Extract Printing. The method of applying a design to dyed fabric by printing a color-destroying agent. Such as chlorine or hydrosulfite, to bleach out a white or light pattern on the darker colored ground. In color-discharge printing, a dye impervious to the bleaching agent is combined with it. It’s producing a colored design instead of white on the dyed ground. Discharge printing is a screen printing process where the same techniques and equipment are used but instead of normal ink, discharge inks are used, which remove the shirt’s dye instead of putting a color on top of the shirt.
It is somewhat similar to bleaching in a design, except it doesn’t damage the fibers like bleaching would. It can be used by itself, as an under base for other colors to be put on top, or with pigments added. Pigmenting discharge could be difficult to achieve exact color results, as the discharge efficacy affects the color, and what you see is not what you get when mixing the pigments, but it can still be a great way to achieve colors on dark garments.
Author of this Article: Rana Sohel Executive Engineer Sunman Textile Mills Ltd. Chittagong Cell: +8801912-420118 Email: [email protected]